THE    SERVICE 


OF 


COAST   ARTILLERY 


BY 

FRANK    T.    MINES 

1  XITED    STATES    ARMY 
Captain,  Coast  Artill*     /  Corps-  Honor  Graduate,  Tnifd  :  '  'tes  Coast  Artillery  S( 


FRANKLIN    \V.    WARD 

NATIONAL  GUARD  OF  NEW  YORK 

Major,  Coast  Artillery  Corps,  Nititft  Artillery  District;  Member  Division  J'J.r<t>ttini>/</  l> 

Artillery  Officers 


PUBLICATION    AUTHORIZED    BY    THE    WAR   DEPARTMENT 


OF   THE 

UNIVERSITY 

OF 


NEW  YORK 
GOODENOUGH  &  WOGLOM  COMPANY 

122  NASSAU  STREET 


GENERAL 


Copyright,  1910, 
By  FRANK    T.    HINES     AND     FRANKLIN    W.    WARD 


All  rights  reserved 


£he  Scientific  f  reas 
Robert  JJrummonb  anft  (Eontpang 


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PREFACE 


FEW  words  are  needed  to  state  the  purpose  of  this  work.  It 
represents  an  earnest  attempt  to  furnish  an  informative  book  for 
the  use  of  coast  artillerists  with  special  reference  to  militia  duty  in 
coast  defense. 

The  organization  of  the  United  States  Coast  Artillery  presents 
a  need  which  the  National  Government  is  not  wholly  able  to  supply. 
The  Coast  Artillery  Corps  of  the  United  States  Army  at  its  present 
strength  cannot  provide  at  the  utmost  for  more  than  one-half  of 
one  manning  detail  for  the  armament  of  our  far-reaching  coast 
fortifications.  To  supply  this  deficiency  in  personnel  Congress  has 
authorized  the  development  of  a  Coast  Artillery  Reserve  to  which 
various  coastwise  states  have  transferred  specially  qualified  regiments 
of  infantry  from  their  militia  organizations. 

In  these  regiments,  and  in  other  organizations  not  so  transferred 
whose  services  will  be  required  as  Coast  Artillery  Supports  and  Coast 
Guard,  are  many  officers  and  men  desirous  of  fitting  themselves  for 
the  technical  service  of  coast  defense.  A  complete  programme  of 
instruction  has  been  issued  by  the  War  Department,  and  it  is  to 
supplement  this,  as  well  as  to  furnish  a  suitable  reference  book  *for 
the  Regular  personnel,  that  the  present  work  was  prepared. 

The  authors  believe  they  have  brought  together  in  simple  form 
and  compact  shape  the  detailed  information  indispensable  to  efficiency 
on  the  part  of  the  coast  artillerist,  be  he  officer  or  man.  In  the 
descriptions  of  armament  and  material,  they  have  held  strictly  to 
information  procured  from  Ordnance  Department  publications;  as 
well  as  Coast  Artillery  orders,  memoranda  and  circulars.  In  most 
cases  the  information  given  here  is  transcribed  from  official  documents. 
No  pretense  is  made  that  the  work  is  exhaustive  or  conclusive,  but 
so  far  as  it  goes  it  has  the  kindly  approval  of  Brigadier-General 
Arthur  Murray,  Chief  of  Coast  Artillery,  and  other  distinguished 
officers  of  the  Army. 

iii 


204111 


IV  PREFACE 

The  authors  indulge  the  hope  that  the  order  and  arrangement  of 
the  text  may  be  helpful  to  every  patriotic  student  of  coast  defense , 
and  if  the  hope  shall  be  realized  they  will  consider  themselves  amply 
repaid  for  their  labors.  Their  thanks  are  due  and  gratefully  tendered 
to  Major  William  G.  Haan,  Coast  Artillery  Corps,  for  his  consistent 
encouragement,  generous  advice  and  valuable  suggestions.  They 
desire  to  express  their  obligations  to  Colonel  Erasmus  M.  Weaver, 
Chief  of  Division  of  Militia  Affairs;  Lieutenant-Colonel  Charles  J. 
Bailey,  Assistant  to  the  Chief  of  Coast  Artillery;  Lieutenant-Colonel 
Adclbert  Cronkhite,  Coast  Defense  Officer,  Department  of  the  East; 
Major  Thomas  W.  Winston,  Coast  Artillery  Corps,  editor  of  the 
Journal  of  the  United  States  Artillery;  and  Mr.  Samuel  L.  Williams. 

It  is  believed  that  this  book  is  better  illustrated  than  any  on  the 
subject  which  has  preceded  it;  an  advantage  mainly  due  to  the  skill 
of  Captain  Bruno  F.  Wetzelberg,  Coast  Artillery  Corps,  N.  G.,  N.  Y., 
by  whom  the  original  photographs  and  many  of  the  drawings  were 
made,  and  to  whom  the  authors  are  deeply  indebted.  They  also  desire 
to  express  their  thanks  to  Master  Gunner  George  D.  Meece,  Coast 
Artillery  Corps,  for  drawings. 

The  volume  has  no  other  motive  than  to  contribute  to  the  efficiency 
of  a  most  important  arm  of  the  United  States  military  service,  The 
United  States  Coast  Artillery  Corps. 

FORT  WADSWORTH,  N.  Y.,  September,  1909. 


CONTENTS 


CHAPTER  I 

DEFINITIONS,  ABBREVIATIONS  AND  SIGNS 

PAGE 

Including  Approved  Interpretations  of  all  Technical  Terms  and  Phrases 
used  in  the  Coast  Artillery  Service,  together  with  Explanations, 
Descriptions  and  Simplified  Outlines  of  all  Elements  of  Coast  Defense 
and  Related  Subjects 1 

CHAPTER  II 
THEORY  AND  PRINCIPLES  OF  COAST  DEFENSE 

Theory  of  Defense,  Attacks  from  Sea,  Plan  of  Land  Defense,  Field  Com- 
bat, Fire  in  Field  Combat  and  Night  Attacks 66 

CHAPTER  III 
ORGANIZATION  AND  PERSONNEL 

The  Tactical  and  Administrative  Organization,  Personnel,  Staff  Officers, 
Coast  Artillery  Reserve  Officers,  Commands  Appropriate  to  Grade,  and 
Non-commissioned  Officers,  etc 76 

CHAPTER  IV 
GUNNERY  AND  BALLISTICS 

Gunnery,  Method  of  Gun  Construction,  Rifling  and  its  Twist,  The  Pro- 
jectile in  the  Gun,  The  Projectile  in  its  Flight  or  the  Trajectory,  Aim- 
ing and  Laying.  Accuracy  of  Fire  and  Practice,  Ballistic  Symbols 
and  Simple  Formulas,  Geometrical  Magnitudes,  etc 79 

CHAPTER  V 
ARMAMENT 

Detailed  Description  and  Classification  of  the  Primary,  Intermediate  and 
Secondary  Armament,  Firing  Mechanisms,  Subcaliber  Guns,  -  Recoil 

Systems,  etc 107 

v 


vi  CONTENTS 

CHAPTER  VI 
EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES 

PAGE 

Low  Explosives,  High  Explosives  and  Fulminates,  their  Chemical  Properties 
and  Method  of  Manufacture.  Preparation  and  Blending  of  Charges, 
Weights,  Velocities,  Pressure,  etc.  Service  Projectiles,  Color  Scheme 
and  Method  of  Painting,  Weights,  Penetration,  etc.  Composition, 
Construction  and  Action  of  all  Types  of  Primers  and  Fuses 245 


CHAPTER  VII 
INSTRUMENTS,  DEVICES  AND  CHARTS 

Depression  Position  Finders,  Telescopes,  Azimuth  Instruments,  Sur- 
veyor's Transit,  Plotting  Boards,  Mortar  Predicter,  Range  Board, 
Deflection  Boards,  Wind  Component  Indicator,  Aeroscope,  Time- 
interval  Clock,  Interrupter,  Telautograph,  Telephone,  Thermometer, 
Mercurial  and  Aneroid  Barometers,  Anemometer,  Atmosphere 
Board,  Open  and  Telescopic  Sights,  Gunner's  Quadrant,  Crusher 
Gauge,  Time-range  Board  and  Powder  Chart 304 


CHAPTER  VIII 
SEARCHLIGHTS 

Tactical  Location  and  Use,  Types  of  Projectors,  Effective  Ranges,  Nomen- 
clature and  Operation 402 

CHAPTER  IX 
SUBMARINE  MINES,  SMALL  BOATS,  ETC. 

Mechanical  and  Electrical  Types  of  Mines,  Mine  Fire-Control  System, 
Mining  Casemate,  Loading  Room,  Method  of  Making  Turk's  Head, 
Telegraph  Joint,  Okonite  Joint,  etc.  Loading  Mines,  Duties  on  the 
Water,  Care  and  Preservation  of  Mine  Material,  Small  Boats  and 
Boat  Drill  . . 414 


CHAPTER  X 
SEACOAST  ENGINEERING 

Theory  of,  Location  and  Measurement  of  Base  Lines,  Triangulation  in 
Connection  with  the  Location  of  Horizontal  Base  Lines,  Gun  Centers 
and  Directing  Points  of  Batteries,  Determination  of  the  True  Azimuth, 
Location  of  Pintle  Centers,  Orientation  of  Gun  and  Mortar  Azimuth 
Circles  (with  problems),  Leveling  and  Hydrographic  Surveying 431 


CONTENTS  vii 

CHAPTER  XI 
CORDAGE 

PAGE 

Types  of  Ropes,  Method  of  Making  Splices,  Knots,  Hitches  and  Straps, 
Blocks  and  Tackle,  Power  of  Tackle,  Levers,  Differential  Pullies, 
Gins,  Shears,  Derricks  and  Cranes,  and  Hydraulic  Jacks 460 

CHAPTER  XII 
MAGAZINE  RIFLE 

Points  in  Handling,  Dismounting  and  Assembling,  Cleaning  and  Care, 
Gun  Sling,  Ammunition,  Ball  Cartridge,  Blank  Cartridge,  Dummy 
Cartridge  and  Guard  Cartridge 483 

CHAPTER  XIII 
POINTS  FOR  COAST  ARTILLERISTS 

Battle  Commanders,  Battle  Command  Drill,  Fire  Commanders,  Fire 
Command  Drill,  Orders  of  Fire,  Searchlight  Commands,  Communica- 
tion Officer,  Battery  Commanders,  Solution  of  Target  Practice 
Problem,  Adjustments  of  Gun  and  Carriage,  Training  of  Personnel, 
Calibration,  Observation  of  Fire,  Emplacement  Officers,  Range  Offi- 
cers, Tug  Officer  and  Observer,  Shore  Tug  Signals,  Maneuver  Signals, 
Sound  Signals,  Wig-wag  Signals,  Night  Signals,  Wireless  Communi- 
cation, Observers,  Gun  Pointers,  Range  Setters,  Meteorological 
Observers,  Tide  Observers,  Camp  Sanitation,  and  Types  of  War 
Vessels .  494 


THE 

SERVICE  OF  COAST  ARTILLERY 


CHAPTER    I 
DEFINITIONS,   ABBREVIATIONS   AND    SIGNS. 

INCLUDING  APPROVED  INTERPRETATIONS  OF  ALL  TECHNICAL  TERMS  AND 
PHRASES  USED  IN  THE  COAST  ARTILLERY  SERVICE,  TOGETHER  WITH 
EXPLANATIONS,  DESCRIPTIONS  AND  SIMPLIFIED  OUTLINES  OF  ALL  ELE- 
MENTS OF  COAST  DEFENSE  AND  RELATED  SUBJECTS. 

"A"  Row.— See  HOOPS. 

Abatis. — In  field  fortification,  rows  of  felled  trees,  with  the  smaller  branches 
lopped  off,  and  the  others  sharpened  and  turned  towards  the  enemy. 

Abbreviations. — See  page  63. 

Absolute  Deviation. — The  distance  measured  in  a  straight  line  from  the 
center  of  the  target  to  the  point  of  impact. 

Accumulator  Room. — A  room  in  the  battery  provided  for  a  storage  battery. 

Adjutant. — See  ARTILLERY  DISTRICT  ADJUTANT,  POST  ADJUTANT. 

Aeroscope. — A  device  used  in  the  meteorological  station  and  the  fire,  mine, 
and  battery  primary  stations  for  the  indication  of  the  azimuth  of  the  wind  in 
in  degrees,  the  velocity  of  the  wind  and  the  density  of  the  atmosphere  by  refer- 
ence numbers.  In  the  latter  stations  it  may  also  contain  a  dial  indicating  the 
height  of  tide. 

Aiming. — The  operation,  with  the  aid  of  a  sight,  of  giving  a  cannon  the 
direction  and  elevation  necessary  to  hit  the  target. 

Air  Spaces. — The  galleries  and  narrow  spaces  around  interior  rooms  to 
facilitate  ventilation  and  assist  in  keeping  the  rooms  dry. 

All-Round-Fire. — Fire  delivered  through  the  entire  circumference  of  an 
azimuth  circle. 

Ammunition. — Any  material  used  in  charging  ordnance,  as  powder,  shot, 
shell,  etc. 

Ammunition  Hoist. — The  device  by  means  of  which  ammunition  is  raised 
to  the  loading  platform.  Separate  hoists  are  used  for  projectiles  and  powder, 
or  the  latter  is  served  by  hand. 

Ammunition  Recess. — The  space  built  in  the  parapet  wall  at  loading  plat- 
form level  for  the  temporary  storage  of  ammunition. 


2  THE  SERVICE  OF  COAST  ARTILLERY 

Ammunition  Shoes. — Any  type  of  slipper  made  entirely  of  a  non-metallic 
substance. 

Ammunition  Truck. — A  steerable  three-wheeled  truck,  with  suitable  space 
for  carrying  a  complete  charge  from  the  delivery  or  reserve  table  to  the  breech 
of  cannon. 

Anemometer. — An  instrument  used  in  the  meteorological  station  to  deter- 
mine the  velocity  of  the  wind  in  miles  per  hour. 

Aneroid  Barometer. — A  watch-shaped  instrument  used  in  the  meteoro- 
logical station  to  determine  the  pressure  or  density  of  the  atmosphere. 

Angle. — The  figure  made  by  two  straight  lines  that  meet  or  would  meet  if 
sufficiently  prolonged,  or,  two  straight  lines  starting  from  the  same  point.  It 
is  measured  by  the  arc  of  a  circle  included  between  its  sides,  the  center  of  the 
circle  being  its  vertex.  An  angle  of  90  degrees  is  known  as  a  right  angle;  an 
angle  of  more  than  90  degrees  is  known  as  an  obtuse  angle;  one  less  than  90 
degrees  as  an  acute  angle. 

Angle  of  Departure. — The  angle  between  the  line  of  departure  and  the  line 
of  sight.  This  is  the  angle  given  in  range  tables.  See  QUADRANT  ANGLE  OF 
DEPARTURE. 

Angle  of  Fall. — The  angle  of  fall  is  the  angle  which  the  tangent  to  the 
trajectory  at  the  point  of  impact  makes  with  the  line  of  shot.  In  practical 
gunnery  the  angle  of  fall  is  often  expressed  as  a  slope,  i.e.,  1  on  10,  meaning 
that  for  one  foot  of  drop  in  vertical  height  the  projectile  would  travel  ten  feet 
horizontally. 

Angle  of  Impact. — The  complement  of  the  angle  of  incidence. 

Angle  of  Incidence. — The  angle  between  the  line  of  impact  and  the  normal 
to  the  surface  at  the  point  of  impact. 

Angle  of  Jump. — See  JUMP,  ANGLE  OF. 

Angle  of  Position  (or  Depression). — The  angle  between  the  line  of  sight 
and  a  horizontal  plane  through  the  axis  of  the  trunnions. 

Angle,  Quadrant. — See  QUADRANT  ANGLE. 

Angle,  Striking. — See  STRIKING  ANGLE. 

Angular  Elevation  or  Depression. — The  angular  elevation  or  depression 
of  the  target  includes  the  depression  due  to  the  curvature  of  the  earth.  It  is 
sometimes  called  position  angle. 

Angular  Velocity. — The  ratio  of  the  angular  travel  or  motion  of  a  body,  to 
the  time  consumed  in  describing  the  angle. 

Approaches. — The  water  area  over  which  the  enemy  may  be  expected.  In 
fortification,  roadways  entering  the  battery  parade. 

Apron. — The  reinforced  concrete  or  metal  portion  of  the  superior  slope  of  a 
parapet  and  the  interior  slope  of  a  mortar  pit  designed  to  protect  against  blast. 
Also  called  blast  slope. 

Arc. — Any  part  of  a  circumference. 

Area. — An  extent  of  surface. 

Armament. — Guns  and  mortars  of  various  sizes  and  powers,  including  their 
carriages.  In  the  coast  artillery  service  armament  is  classified  as  primary, 
in  ermediate,  arid  secondary. 

Armor. — The  protection  afforded  the  sides  and  decks  of  warships.  It  is 
classified  as  wrought  iron,  compound,  all  steel  and  face-hardened  armor. 

Armor  Belt. — The  side  protection  of  the  vitals  of  warships. 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  3 

Armor-Piercing  Projectiles. — Shot  and  shell  designed  to  penetrate  heavy 
side  and  turret  armor  of  war  vessels. 

Armstrong  Guns. — The  built-up  gun  construction  of  Great  Britain,  the 
germ  of  which  is  to  be  found  in  the  coiled  welded  system  of  Sir  William  Arm- 
strong, introduced  in  1852. 

Armstrong  Rapid-Fire  Gun. — A  seacoast  cannon  usually  40  to  50  calibers 
long  and  of  6-inch  and  4.72-inch  caliber.  The  latter  is  usually  called  "four 
point  seven. " 

Artillery. — The  name  given  to  all  firearms  discharged  from  carriages  ashore 
in  contradistinction  to  "small  arms,"  which  are  discharged  from  the  hands. 
It  also  denotes  the  particular  troops  employed  in  the  service  of  such  fire- 
arms. 

Artillery  in  the  U.  S.  military  service  is  known  as  coast  artillery  and  field 
artillery,  the  latter  being  classified  as  light  artillery,  horse  artillery,  siege  artillery, 
and  mountain  artillery. 

Artillery  District. — An  artillery  district  is  a  subdivision  of  the  coast  line, 
including  the  entire  personnel  of  coast  artillery  troops  proper,  and  coast  artillery 
supports  assigned  to  duty  in  connection  with  the  fixed  defenses  thereof. 

For  tactical  purposes  it  consists  of  those  battle  commands  which  are  within 
supporting  distance  of  one  another. 

For  administrative  purposes,  forts  not  within  supporting  distance  may  be 
included  in  the  district. 

In  the  regular  service,  districts  are  designated  by  name,  as  "  Eastern  Artil- 
lery District  of  New  York, "  "Artillery  District  of  the  Columbia/'  etc.  In  the 
organized  militia  it  is  customary  to  designate  them  by  number,  as  "Thirteenth 
Artillery  District,  N.  G.,  N.  Y." 

Artillery  District  Adjutant. — A  coast  artillery  officer  responsible,  under 
the  district  commander,  for  the  various  reports,  returns,  rosters,  details,  records, 
orders  and  communications  pertaining  to  the  administration  of  an  artillery  dis- 
trict, together  with  all  other  duties  prescribed  for  regimental  adjutants  so  far 
as  they  are  applicable  to  artillery  districts.  His  tactical  duties  are  those  of  a 
communication  officer  of  a  battle  command,  unless  otherwise  assigned  by  the 
district  commander. 

Artillery  District  Commander. — District  commanders  are  assigned  to 
artillery  districts  in  orders  from  the  War  Department.  The  command  of  an 
artillery  district  devolves  upon  the  senior  regular  coast  artillery  officer  present, 
whether  he  has  been  assigned  in  orders  or  not.  However,  with  the  sanction  of 
higher  authority  a  district  commander  may  continue  to  exercise  the  more 
important  functions  of  his  command  when  absent  temporarily  from  his  district 
on  artillery  duty. 

The  district  commander  assigns  field  officers  as  battle,  fire  and  mine  com- 
manders, and  staff  officers  as  searchlight  and  communication  officers.  In 
detailing  officers  other  than  staff  officers  as  searchlight  and  communication 
officers  no  battery  should  be  left  with  less  than  the  number  of  officers  required 
by  its  manning  table.  If  officers  are  not  available,  non-commissioned  officers 
should  be  detailed. 

The  district  commander  is  responsible  for  the  efficiency  of  his  district.  He 
has  control  within  its  limits  of  all  matters  relating  to  artillery  instruction,  drill 
and  practice,  and  is  responsible  for  the  procurement  of  the  proper  supplies  and 


4  THE  SERVICE  OF  COAST  ARTILLERY 

accessories.  He  sees  that  orders  prescribing  drills  and  other  exercises  are 
properly  and  uniformly  carried  out. 

Accompanied  by  members  of  his  staff,  he  inspects  all  forts  in  his  district  at 
prescribed  periods.  During  the  period  for  out-door  instruction  he  inspects  all 
armament,  fire-control  equipment,  light  equipment,  all  necessary  material  and 
fort  record  books  and  battery  emplacement  books.  On  these  occasions  the 
personnel  are  required  to  be  at  their  posts  and  the  inspection  includes  drills  of 
the  various  elements  of  the  defense,  as  well  as  the  physical  condition,  clothing 
and  equipment  of  the  personnel. 

Within  the  time  specified  in  orders  after  the  last  inspection  of  each  quarter, 
he  submits  his  quarterly  report  on  the  prescribed  form,  through  military  chan- 
nels, to  The  Adjutant  General  of  the  Army. 

The  operation  of  all  means  of  water  transportation,  assigned  by  competent 
authority,  for  exclusive  use  of  the  artillery  district,  including  harbor  vessels, 
tugs,  lighters,  dispatch  boats  and  landings  is  under  his  supervision.  He  sees 
that  economy  is  exercised  in  their  maintenance  and  operation.  He  makes  the 
-official  visits  required  to  foreign  and  naval  officers  visiting  in  the  harbor. 

He  conducts  combined  artillery  drill  and  tactical  exercises  of  all  the  elements 
of  defense  of  his  district,  in  accordance  with  existing  orders. 

He  regulates  the  boat  service  so  that  a  target  may  be  towed  one  day  each 
week  for  each  post  during  the  out-door  period. 

He  is  charged  with  the  preparation  of  all  plans  of  defense  for  his  district 
against  hostile  attack,  and  forwards  a  copy  thereof  through  military  channels, 
to  the  Chief  of  Coast  Artillery,  for  approval  and  makes  such  suggestions  as  to 
the  modification  thereof  as  may,  in  his  opinion,  be  required  by  new  conditions. 

He  should  have  knowledge  of  the  plans  of  the  general  defense  of  the  coast 
line  in  the  vicinity  of  his  district  and  be  instructed  by  the  general  officer  com- 
manding as  to  his  duties  in  connection  therewith. 

During  hostilities  he  is  charged  with  the  supervision  of  all  military  operations 
in  his  district  and  in  connection  therewith.  He  establishes  and  maintains  a 
system  of  security  and  information  on  both  the  water  and  land  fronts.  He 
keeps  the  various  subordinate  commanders  informed  as  to  conditions.  He 
appoints  the  artillery  district  staff  officers;  and  upon  proper  recommendation 
and  examination  appoints  the  non-commissioned  officers  and  men  of  the  several 
grades  and  ratings  serving  in  companies,  in  the  district. 

In  the  organized  militia  the  commanding  officer  of  an  organization  assigned 
to  the  coast  artillery  reserve,  when  at  home  station,  receives  this  title. 

Artillery  District  Commander's  Flag. — See  FLAG  OF  ARTILLERY  DIS- 
TRICT COMMANDER. 

Artillery  District  Engineer. — See  DISTRICT  ARTILLERY  ENGINEER. 

Artillery  District  Ordnance  Officer. — A  coast  artillery  officer  charged  with 
the  requisition,  accountability,  inspection  and  repair  of  all  ordnance  property 
and  stores  pertaining  to  the  seacoast  armament  and  equipment  of  an  artillery 
district.  He  has  immediate  supervision  and  control  of  the  district  machine 
shop  and  resident  machinists.  His  tactical  duties  may  be  those  of  communi- 
cation or  searchlight  officer  of  a  battle  command,  unless  otherwise  assigned  by 
the  district  commander. 

Artillery  District  Quartermaster. — An  officer  of  the  Quartermaster's 
Department,  or  a  coast  artillery  officer,  who  is  accountable  and  responsible  for 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  5 

all  quartermaster  property  used  in  connection  with  district  headquarters,  and 
all  water  transportation  assigned  for  use  of  the  artillery  district,  including 
harbor  vessels,  etc.  Under  the  district  commander  he  is  responsible  for  their 
maintenance  and  supply,  personnel,  and  operation.  If  a  coast  artillery  officer, 
his  tactical  duties  are  prescribed  by  the  district  commander. 

Artillery  Engineer. — See  DISTRICT  ARTILLERY  ENGINEER. 

Artillery  Garrison. — The  personnel  assigned  to  duty  at  a  coast  artillery  fort. 

Atmosphere  Board. — A  device  pertaining  to  the  equipment  of  the  meteor- 
ological station.  A  graphic  table  by  means  of  which  the  reference  numbers  to 
be  recorded  on  the  dial  of  the  aeroscope  indicator  can  be  determined  from  read- 
ings of  the  barometer  and  thermometer. 

Automatic  Firing. — A  term  applied  to  one  of  three  methods  of  exploding 
submarine  mines,  i.e.,  where  the  apparatus  is  so  arranged  that  the  mine  ex- 
plodes upon  contact. 

Automatic  Machine  Guns. — Rapid-fire  guns  in  which  the  force  of  recoil  is 
used  to  operate  the  breechlock  and  to  load  and  fire  the  piece. 

Auxiliary  Horizontal  Base  System. — When  either  the  battery  primary 
or  secondary  station  becomes  inoperative,  the  battery  commander's  station  is 
used  as  a  base  end  station  in  place  of  the  disabled  station. 

Auxiliary  Power  Plant. — See  SECONDARY  OR  AUXILIARY  POWER  PLANT. 

Axial  Vent. — A  vent  in  which  the  opening  is  parallel  with  the  axis  of  the 
bore.  It  is  the  type  of  vent  used  in  modern  seacoast  cannon. 

Axis. — A  straight  line,  real  or  imaginary,  passing  through  a  body,  on  which 
it  revolves  or  may  be  supposed  to  revolve. 

Axis  of  Gun. — The  axis,  or  central  line,  of  the  bore. 

Axis  of  Trunnions. — That  axis,  or  central  line  of  the  trunnions. 

Azimuth  of  a  Point. — In  coast  artillery,  the  horizontal  angle  measured 
in  a  clockwise  direction  from  south  to  a  line  from  the  observer  to  the  point. 
For  example,  the  azimuth  of  a  point  R  from  A  is  the  angle  (measured  clockwise 
from  the  south)  between  the  north  and  south  line  through  A  and  the  line  from  A 
to  B.  The  north  point  has  an  azimuth  of  180  degrees. 

Azimuth  Difference. — The  difference  between  two  azimuths  of  a  point  as 
read  from  two  other  points,  as,  for  example,  the  difference  between  the  azimuth 
of  the  target  as  read  from  the  primary  station  and  the  azimuth  of  the  target  as 
read  from  the  directing  gun  or  point  of  a  battery. 

Azimuth  Instrument. — An  instrument  for  determining  azimuths.  It  is 
sometimes  used  as  a  position-finding  instrument  in  secondary  stations. 

Azimuth  Setter. — The  member  of  a  mortar  detachment  who  lays  the 
mortar  in  azimuth. 

"B"  Row.— See  HOOPS. 

Backlash. — The  play  between  a  screw  and  its  nut  where  the  latter  is  loosely 
fitted.  A  reverse  movement  of  any  part  of  a  mechanical  gear,  caused  by 
irregularities,  without  moving  other  connecting  parts. 

Bale. — That  part  of  an  assembled  submarine  mine  used  for  the  attachment 
of  the  mooring  cable  to  the  mine  case ;  also  provided  for  the  protection  of  the 
joint  where  the  single  conductor  cable  enters  the  mine. 

Ballistic  Board.  See  RANGE  BOARD. — A  device  used  to  determine  the 
total  range  corrections  to  be  applied  to  the  range  found  on  the  plotting  board. 

Ballistic  Tables. — Tables  of  data  used  in  connection  with  ballistic  formula 


6  THE  SERVICE  OF  COAST  ARTILLERY 

in  the  solution  of  ballistic  problems;  certain  functions  used  in  the  various 
formulas  are  previously  calculated  for  the  certain  velocities  and  then  tabulated. 

Ballistics. — That  branch  of  the  science  of  gunnery  which  treats  of  the  motion 
of  projectiles. 

Bandoleer. — A  khaki-colored  small  arms  ammunition  belt,  consisting  of 
six  pockets,  each  containing  two  clips  or  ten  rounds.  Worn  over  one  shoulder 
and  under  the  opposite  arm. 

Banquette. — The  step  between  the  truck  and  loading  platform. 

Banquette  Tread. — In  field  fortification,  a  tread  or  foot  bank  running 
along  the  inside  of  the  interior  slope  upon  which  soldiers  stand  to  fire  over  the 
parapet. 

Bar  and  Drum  Sight. — An  open  sight  used  on  rapid-fire  guns. 

Barbette. — A  mound  of  earth  or  a  platform  on  which  guns  are  mounted  to 
fire  over  a  parapet.  In  field  fortification  this  level  is  distinguished  by  the 
name  of  Banquette  Tread. 

Barbette  Carriage. — See  CARRIAGE  OR  MOUNT. 

Barometer. — See  ANEROID  BAROMETER  and  MERCURIAL  BAROMETER. 

Base-end  Station. — An  observing  station  located  at  either  end  of  a  base 
line,  designed  to  contain  an  azimuth  instrument  or  depression  position  finder. 
Base-end  stations  are  designated  as  primary,  secondary,  or  supplementary. 

Base  Fuse. — A  firing  device  inserted  in  the  base  of  cored  shot  and  armor- 
piercing  shell  to  ignite  the  bursting  charge.  Base  fuses  are  used  when  the 
point  of  shell  requires  great  strength,  as  for  penetrating  armor. 

Base  Line. — A  horizontal  line  the  length  and  direction  of  which  has  been 
determined.  This  line  is  used  in  position  finding,  especially  for  long  ranges ; 
the  stations  at  its  ends  are  called  base-end  stations.  It  is  called  "right"  or 
"  left "  handed,  depending  on  whether  the  primary  station  is  to  the  right  or  left 
of  the  secondary  facing  the  field  of  fire. 

Battery. — The  entire  structure  erected  for  the  emplacing,  protection  and  ser- 
vice of  one  or  more  guns  or  mortars,  together  with  the  guns  and  mortars  so 
protected.  The  guns  of  a  battery  are  of  the  same  size  and  power,  and  are 
grouped  with  the  object  of  concentrating  their  fire  on  a  single  target  and  of  their 
being  commanded  directly  by  a  single  individual. 

Normally  a  battery  of  the  primary  armament  consists  of  two  guns  or  two 
pits  of  mortars.  Under  exceptional  circumstances  a  single  gun  with  its  fire- 
control  service  may  constitute  a  battery. 

In  the  case  of  intermediate  and  secondary  armament  a  battery  may  consist 
of  any  number  of  guns  assigned  to  it. 

Battery  Commander. — The  senior  artillery  officer  present  for  duty  at  a 
battery. 

The  battery  commander  exercises  both  administrative  and  tactical  command. 

As  an  administrative  officer  he  is  responsible  that  every  effort  is  made  to 
keep  the  battery  supplied  with  the  proper  equipment,  implements  and  ammu- 
nition. He  keeps  a  record  of  the  daily  attendance  at  drill  and  instruction,  with 
names  of  absentees,  reason  and  authority  for  such  absence. 

As  a  tactical  officer  he  is  responsible  that  the  personnel  of  his  battery  is 
efficient  in  drill,  in  practice  and  in  action,  that  the.equipment  and  fire-control 
installation  provided  for  his  battery  are  in  serviceable  condition  and  that  no 
permanent  modifications  are  made  therein  without  proper  authority.  He  is 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  7 

required  to  see  that  the  officers  and  men  of  his  battery  are  instructed  in  the  care, 
preservation  and  use  of  artillery  material,  and  that  records  are  kept  and  reports 
rendered  as  prescribed  in  orders  and  regulations. 

He  is  authorized  to  modify  the  manual  of  the  piece  within  the  limits  pre- 
scribed by  the  drill  regulations  and  to  make  temporary  modifications  or  changes 
ia  the  fire-control  installation,  provided  such  modifications  or  changes  per- 
mit of  prompt  return  to  their  original  condition.  Permanent  changes  may  be 
made  in  the  provisional  installations  upon  the  approval  of  the  district  com- 
mander, the  changes  to  be  reported  to  the  War  Department.  Changes  in  the 
standard  installation  can  only  be  made  with  the  approval  of  the  War  Depart- 
ment. 

He  should  be  encouraged  by  his  superiors  to  improvise  devices  and  methods 
that  will  simplify  the  fire-control  system  or  increase  the  efficiency  of  his 
command. 

He  is  responsible  that  the  plotting-room  details  for  the  fire  and  battle 
commanders'  stations  are  kept  in  practice  during  the  period  of  indoor  instruction. 

He  should  inspect  his  battery  and  make  a  test  of  the  fire-control  system 
thereof  weekly. 

In  battle  command  or  fire  command  drill  or  action  he  exercises  limited 
fire  control,  acting  on  orders  received  from  higher  commanders.  When  "  battery 
commander's  action"  is  ordered  he  exercises  independent  fire-control  and 
fights  his  battery  in  accordance  with  his  own  judgment.  In  cases  of  emergency 
he  acts  without  waiting  for  orders,  in  accordance  with  instructions  previously 
given. 

Battery  Commander's  Station. — An  observing  station  at  or  near  the  battery, 
usually  in  rear  of  the  center  traverse.  The  new  type  is  a  combined  observing 
room,  emergency  instrument  room,  plotting  room,  etc.,  at  the  rear  of  the 
traverse. 

Battery  Commander's  Walk. — The  elevated  walk  leading  from  the  battery 
commander's  station  along  the  rear  of  the  battery. 

Battery  Emplacement  Book. — A  loose-leaf  record  book  provided  for  each 
battery,  in  which  all  important  data  relating  to  the  emplacements,  guns,  fire- 
control  equipment,  etc.,  of  a  battery  are  kept. 

Battery  Field  of  Fire. — The  area  covered  by  the  armament  of  a  battery; 
it  covers  that  portion  of  the  fire  area  which  can  be  most  conveniently  defended 
by  the  battery  in  question. 

Battery  Manning  Table. — A  table  containing  a  list  of  names  detailing 
the  personnel  of  a  battery  to  their  posts. 

Battery  Parade. — The  area  in  rear  of  the  emplacements  of  a  battery  where 
the  sections  form. 

Battle  Area. — The  area  covered  by  the  armament  of  a  battle  command. 

Battle  Chart. — A  chart  used  in  battle,  fire,  and  mine  command  stations 
which  covers  their  respective  areas.  It  is  constructed  to  show  the  channels 
and  different  depths  of  water  passable  by  the  several  types  of  war  vessels;  i.e., 
the  sector  of  any  water  area  navigable  by  battleships,  cruisers,  torpedo 
boats  and  smaller  craft.  It  also  shows  the  sectors  of  fire  of  the  several  batteries 
in  the  particular  command,  and  in  the  case  of  mine  commands  the  position  of 
the  fields,  etc.  It  also  sho^s  the  penetration  in  Krupp  armor  for  each  1,000 
yards  of  range  for  the  several  classes  of  armament.  It  is  provided  with  an 


8  THE  SERVICE  OF  COAST  ARTILLERY 

azimuth  circle  the  center  of  which  marks  the  location  of  the  station  to  which 
the  chart  belongs. 

Battle  Command. — A  battle  command  includes  that  portion  of  the  arma- 
ment assigned  to  any  particular  portion  of  the  water  area  of  an  artillery  district 
in  which  a  naval  attack  may  be  expected  and  over  which  one  man  may  exercise 
efficient  control  of  the  artillery  fire  and  other  means  provided  for  defense. 

Two  or  more  fire  commands  and  one  mine  command  usually  constitute  a 
battle  command.  There  may  be  one  or  more  battle  commands  in  an  artillery 
district. 

Two  or  more  artillery  forts  or  posts  situated  so  that  their  armament  covers 
the  same  or  adjacent  water  areas  may  constitute  one  battle  command. 

Responsibility  for  the  sufficiency  and  condition  of  the  material  of  a  battle 
command  devolves  upon  the  commanding  officers  of  districts  or  posts  in  which 
the  battle  command  is  located. 

Battle  Commander. — A  coast  artillery  officer  assigned  as  such  in  orders 
from  district  headquarters.  He  commands,  for  tactical  purposes  only,  the 
personnel  of  a  battle  command  and  is  responsible  for  its  tactical  efficiency. 

A  battle  commander  sees  that  all  orders  prescribing  battle-command  driUs 
and  other  exercises  are  properly  and  uniformly  carried  out.  By  frequent  visits 
to  the  fire  commands  he  keeps  posted  as  to  the  condition  of  the  material  and 
personnel,  so  as  to  be  able  to  report  at  all  times  as  to  their  drill  efficiency  and  the 
condition  of  his  battle-command  service.  He  should  exercise  in  battle-command 
drill  and  in  action,  fire  control  throughout  his  command  and  over  the  battle 
area,  and  command  the  fire  action  from  his  station — from  which  the  whole 
battle  area  and  approaches  thereto  should  be  visible. 

He  should  have  full  knowledge  of  the  nature  and  position  of  the  mine  fields 
and  any  obstructions  in  his  battle  area  and  should  be  in  communication  with 
the  district  commander,  and  his  fire  and  mine  commanders.  He  should  be 
informed  of  the  general  scheme  of  land  defense,  and  after  a  careful  study -of  his 
battle  area,  prepare  plans  of  defense  against  the  forms  of  attack  liable  to  be 
adopted  by  the  enemy.  He  should  be  prepared  to  prevent  reconnaissance  in 
force  on  the  part  of  the  enemy  calculated  to  determine  the  strength  and  location 
of  the  batteries. 

At  night  the  searchlights  assigned  to  his  battle  area  are  under  his  immediate 
control.  Searchlights  intended  primarily  for  the  mine  service  remain  ordinarily 
under  the  control  of  the  mine  commander,  but  when  the  battle  commander 
deems  it  necessary  to  use  a  mine-field  light  for  searching,  such  light  is  under 
control  of  the  searchlight  officer  temporarily. 

Battle  Commander's  Station. — A  station  overlooking  a  battle  area,  occupied 
by  the  battle  commander,  and  necessary  assistants,  during  drill  or  action. 

Battle  Flag. — The  national  flag  (garrison  flag)  displayed  at  a  seacoast  or  lake 
fort  at  the  beginning  of  and  during  an  engagement,  whether  by  day  or  night. 
It  is  also  flown  from  the  mainmast  of  vessels  engaged. 

Battleships. — War  vessels  of  massive  appearance  with  broad  beam  as 
compared  with  length.  They  have  heavily  armor-plated  turrets  and  belt  from 
8  to  18  inches  in  thickness;  deck  and  other  armor  3  to  6  inches  in  thickness. 
Average  displacement  10,000  to  26,000  tons;  length  375  to  550  feet;  beam  60 
to  75  feet;  draft  24  to  30  feet;  speed  16  to  21  knots  (the  measure  of  a  nautical 
mile  or  knot  is  6080.27  feet,  as  against  a  statute  mile,  which  measures  5280  feet). 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  9 

Armament  consists  of:  Main,  14-inch,  13-inch,  12-inch.  Intermediate,  8-inch, 
7-inch,  6-inch  guns,  and  torpedo  tubes.  Secondary,  3-inch  and  smaller  rapid- 
fire  guns. 

Battle  Tactics. — As  pertaining  to  fortress  warfare,  the  science  of  the 
disposition  and  handling  of  coast  artillery  units  in  action. 

Berm. — In  field  fortification,  a  moulding  of  natural  ground  between  the 
foot  of  the  exterior  slope  and  the  scarp. 

Bevel  Wheel. — A  wheel  having  teeth  cut  on  a  bevel  or  conical  surface  called 
a  face ;  where  the  inclination  of  the  face  is  45  degrees  it  is  called  a  miter  wheel. 
Two  of  these  wheels  with  teeth  engaged  at  right  angles  to  each  other  form  a 
bevel  or  miter  gear. 

Bivouac. — A  temporary  place  of  repose  for  troops,  in  which  they  are  shel- 
tered by  shelter-tents,  bowers,  or  improvised  shelter  of  any  kind,  or  sleep  in  the 
open  air. 

Blast. — See  POWDER  BLAST. 

Blast  Slope  or  Apron. — See  APRON. 

Blasting-Gelatine. — The  most  powerful  of  the  detonating  and  disrupt"' ve 
explosives.  It  is  only  suitable  for  purposes  of  demolition. 

Blending  Powder. — The  process  of  mixing  powders  of  the  same  or  different 
lots  so  as  to  obtain  charges  of  uniform  characteristics. 

Blending  Room. — A  dry,  well-lighted  and  ventilated  room  in  which  several 
charges  of  the  same  lot  of  smokeless  powder  are  taken  from  the  powder  storage 
cases  and  thoroughly  mixed  and  blended. 

Blind  Shell. — A  shell  which  does  not  explode  upon  impact  or  when 
intended  to  do  so. 

Boat  Telephone. — A  simple  type  of  telephone  used  in  communicating  over 
cable  between  boats  at  distribution  boxes  in  the  mine  field  and  the  mining 
casemate. 

Bomb. — A  missile  which  also  receives  the  names  of  bombshell  and  shell. 
The  use  of  the  word  is  practically  obsolete  in  gunnery. 

Bomb-Proof. — A  term  applied  to  military  structures  of  such  immense 
thickness  and  strength  that  shells  can  not  penetrate  them. 

Booth  or  Recess. — Any  recess  or  construction  for  the  accommodation  of 
telautograph,  telephone,  etc. 

Bore. — The  interior  of  a  cannon  forward  of  the  front  face  of  the  breech 
block.  It  is  composed  of  the  powder  chamber,  the  centering  slope,  the  forcing 
cone,  and  the  rifled  portion,  called  the  main  bore. 

Bore,  Length  of. — See  LENGTH  OF  BORE. 

Bore-Plug. — See  CLINOMETER  REST. 

Bore-Sighting. — In  coast  artillery,  the  process  by  which  the  line  of  sight 
and  axis  of  the  bore  prolonged  are  caused  to  converge  on  a  point  at  or  beyond 
mid-range. 

Bottom  of  the  Bore. — The  surface  of  the  powder  chamber  formed  by  the 
face  of  the  obturator-head  when  the  breech-plug  is  home. 

Bound. — The  path  of  a  shot  comprised  between  two  grazes. 

Bourrelet. — That  part  of  a  projectile  between  the  main  body  and  the  head, 
which  includes  the  beginning  of  the  ogive. 

Brackets. — Metal  supports  for  telautograph  cases,  etc. 

Breech. — The  mass  of  metal  behind  the  plane  of  the  bottom  of  the  bore. 


10  THE  SERVICE  OF  COAST  ARTILLERY 

Breechblock. — The  metal  plug  which  closes  the  breech. 

Breech  Bushing. — That  part  of  the  breech  which  contains  the  threaded 
and  slotted  sectors  of  the  breech  recess. 

Breech  Detail. — A  detail  of  the  gun  detachment  charged  with  the  duty  of 
opening  and  closing  the  breech. 

Breech,  Face  of — See  FACE  OF  BREECH. 

Breech  Mechanism. — The  breechblock,  obturating  device,  firing  mechanism, 
and  mechanism  for  operating  the  breechblock. 

Breech  Recess. — That  part  of  the  cannon  which  receives  the  breechblock. 

Breech  Reinforce. — The  part  of  the  cannon  in  front  of  the  breech  and  in 
rear  of  the  trunnion  band. 

Brown  Prismatic  Powder. — A  brown  gunpowder  of  translucent  celluloid 
appearance,  in  the  form  of  a  six-sided  prism  with  a  hole  in  the  center. 

Building  up  Charges. — The  operation  of  preparing  charges  of  brown  pris- 
matic, nitro-cellulose  or  spero-hexagonal  powder,  by  properly  placing  the 
grains  in  silk  bags. 

Built-up  Cannon. — Types  of  cannon  in  which  the  parts  are  built  up  of 
either  cylindrical  forgings  or  a  single  forging  wrapped  with  a  rectangular  Or 
ribbon  form  of  wire. 

Buoy. — A  floating  object  moored  to  the  bottom,  used  for  temporarily 
marking  the  positions  of  mines,  junction  and  distribution  boxes,  channels,  and 
target  positions. 

Bursting  Charge  or  Shell  Filler. — The  charge  of  explosive  required  for 
bursting  a  projectile ;  it  may  be  poured  in  loose  or  by  melting. 

Butt. — In  gunnery,  a  solid  earthen  parapet,  to  fire  against  in  the  proving 
grounds  or  in  practice. 

Button  Drill  Primer. — A  form  of  primer  so  called  from  the  fact  that  the 
head  of  the  friction  wire  is  formed  in  the  shape  of  a  button. 

"  C  »  Row.— See  HOOPS. 

Cake  Powder. — Gunpowder  which  has  become  lumpy  from  having  absorbed 
moisture. 

Caliber. — A  name  given  the  minimum  diameter  of  the  bore  of  a  firearm; 
it  is  the  diameter  of  the  main  bore  in  inches  measured  at  the  top  of  diametrically 
opposite  lands,  or  minimum  diameter  of  the  rifled  portion  of  ihe  bore.  Also 
used  to  express  the  length  of  cannon;  e.g.,  a  12-inch  gun  42  calibers  long 
would  be  42  feet  long ;  a  6-inch  gun  52  calibers  long  would  be  26  feet  long. 

Calibration. — The  operation  of  adjusting  the  range  scale  so  that  the  range 
reading  at  any  particular  elevation  of  the  gun  will  indicate  the  true  distance 
to  the  center  of  impact  of  a  group  of  shots  fired  from  that  particular  gun  and 
mount  at  that  elevation  with  the  standard  velocity  and  under  normal  atmos- 
pheric conditions. 

It  is  desirable  to  calibrate  the  guns  of  a  battery  under  the  same  atmospheric 
conditions,  although  this  is  not  absolutely  necessary.  It  is  absolutely  necessary 
that  uniform  ammunition  be  used  for  calibration  firing  of  all  guns  of  a  particular 
battery.  When  the  individual  guns  of  a  battery  are  calibrated  the  battery  is 
calibrated,  for  the  centers  of  impact  of  a  series  of  shots  from  each  gun  under 
normal  atmospheric  conditions  will  coincide  at  the  point  indicated  by  any 
range  setting.  When  guns  of  a  battery  "  shoot  together  "  (that  is,  give  the  same 
range  for  the  same  range  setting)  they  may  be  fired  on  the  same  data,  but  are 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  11 

not  calibrated  unless  the  range  under  normal  atmospheric  conditions  is  that 
indicated  by  the  range  setting. 

It  is  not  feasible  to  dete  mine  by  actual  firing  all  the  points  of  a  range  scale, 
and  therefore  it  is  assumed  that  the  gun  is  calibrated  when  a  range  scale  con- 
structed from  a  computed  range  table  is  adjusted  on  the  gun  so  as  to  give  the 
proper  setting  for  a  mid-range. 

Call  to  Arms. — A  musical  signal  at  which,  if  practicable,  each  man  goes 
direct  to  his  post  at  a  run. 

Cannister. — A  projectile  with  a  thin  wall  inclosing  a  number  of  small  steel 
balls  but  without  a  bursting  charge,  the  case  being  ruptured  by  the  shock  of 
discharge  as  the  projectile  leaves  the  gun.  Designed  for  use  against  infantry 
at  short  range. 

Cannon. — A  general  term  for  artillery  weapons  and  firearms  not  carried  nor 
fired  in  the  hands,  from  which  projectiles  are  thrown  by  the  force  of  expanding 
powder  gases. 

Guns  are  long  (generally  from  30  to  50  calibers)  have  flat  trajectories,  and 
are  used  for  low-angle  fire  (less  than  15  degrees),  with  high  velocities  (from 
2000  to  3000  f.s.,  about). 

Mortars  are  short  (generally  about  10  calibers),  and  are  used  for  high-angle 
fire  (from  45  degrees  to  70  degrees),  with  low  velocities  (from  550  to  1300  f.s., 
about) . 

Howitzers  are  intermediate  between  guns  and  mortars. 

The  term  " piece"  is  used  when  referring  to  a  cannon  of  any  class.  Cannon 
in  the  United  States  land  service  are  classified  according  to  their  use  into  coast, 
siege,  and  field. 

Cannon  Ball. — Properly  speaking,  this  term  should  only  be  applied  to 
spherical  solid  projectiles  which  are  fired  from  cannon. 

Cannon  Powder. — A  term  applied  to  large-grained  black  or  brown  gun- 
powder to  distinguish  it  from  rifle,  mortar  or  mammoth  powder.  It  is  used 
as  a  base  in  the  manufacture  of  prismatic  powders. 

Cannonade. — The  act  of  discharging  shot  and  shell  from  cannon  for  the 
purpose  of  destroying  an  enemy.  To  discharge  cannon.  Also  written  can- 
nonry. 

Cannoneer. — An  artilleryman  engaged  in  the  firing,  or  one  who  manages  or 
assists  in  managing  a  cannon. 

Canopy. — The  projecting  roof  over  delivery  tables  of  ammunition  hoists  of 
modernized  gun  batteries. 

Cap-Square. — That  portion  of  the  iron  work  of  a  gun  or  mortar  carriage 
which  folds  or  laps  over  the  exterior  portion  of  the  trunnions  to  keep  the  piece 
from  jumping  out  of  the  trunnion  bed. 

Capital. — The  line  through  the  gun  pintle  perpendicular  to,  or  bisecting  the 
arc  of  the  interior  crest. 

Capped  Projectile. — A  projectile  having  a  soft  iron  cap  over  its  point  to 
give  stability  to  the  point  when  commencing  penetration  and  to  give  the  armor 
an  initial  pressure  at  the  point  of  penetration. 

Carriage  or  Mount. — The  means  provided  for  supporting  a  cannon.  It 
includes  the  parts  for  giving  elevation  and  direction,  for  taking  up  the  recoil 
on  discharge,  and  for  returning  the  piece  to  the  firing  position.  They  are 
classified  as  follows: 


12  THE  SERVICE  OF  COAST  ARTILLERY 

1.  Fixed.     A  mount  provided  for  guns  and  mortars  in  permanent  works 
and  not  designed  to  be  moved  from  place  to  place. 

2.  Movable   or    Wheeled.     A  carriage  or  mount  provided  with  wheels  for 
ready  transportation  of  the  piece  mounted  thereon.     Guns  of  the  movable 
armament  are  mounted  on  this  type  of  carriage. 

COAST  CARRIAGES.  Those  used  for  coast  artillery  cannon.  They  may  be 
divided  into  four  classes,  depending  upon  the  nature  of  cover  afforded  by  the 
emplacements : 

a.  Barbette.     Where  the  gun  remains  above  the  parapet  for  loading  and 
firing. 

b.  Disappearing.     Where  the  gun  is  raised   above  the  parapet  for  firing, 
and  recoils  under  cover  for  loading. 

c.  Masking  mount.     Where  the  gun  remains  above  the  parapet  for  loading 
and  firing  but  can  be  lowered  below  the  level  of  the  crest  for  concealme-it. 

d.  Casemate.     Where  the  gun  fires  through  a  port. 

RAPID-FIRE  GUN  CARRIAGES  (except  the  6-inch  on  disappearing  carriage) 
are  constructed  so  that  the  gun  recoils  in  a  sleeve  and  returns  to  the  loading 
position  immediately  after  firing. 

Note. — If  the  carriage  can  be  traversed  so  that  the  gun  may  be  fired  in  all 
directions  it  is  said  to  have  all-round  fire.  If  it  can  not  be  traversed  so  that 
the  gun  can  be  fired  in  all  directions,  it  is  said  to  have  limited  fire. 

Cartridge. — A  complete  charge  contained  in  or  held  together  by  a  case  or 
shell  of  metal. 

Cartridge  Bags. — Bags  made  of  a  special  quality  of  silk  and  sewed  with 
silk  thread;  used  to  contain  the  powder  charge  for  cannon.  This  material 
burns  rapidly  and  completely,  thus  avoiding  the  danger  of  a  smouldering 
residue  in  the  powder  chamber. 

Cartridge  Extractor. — That  part  of  a  breech-loading  gun  which  ejects  the 
empty  cartridge  case  from  its  seat  in  the  bore. 

Cartridge  Room. — A  room  of  the  magazine  for  the  storage  of  cartridges. 

Case. — The  charge  holder  of  a  submarine  mine. 

Case  I. — In  gunnery,  a  class  of  gun  pointing  where  direction  and  elevation 
are  both  given  by  the  sight. 

Case  II. — In  gunnery,  a  class  of  gun  pointing  where  direction  is  given  by 
the  sight  and  elevation  by  the  range  scale  on  the  carriage. 

Case  III. — In  gunnery,  a  class  of  gun  pointing  where  direction  is  given  by 
the  azimuth  scale  and  elevation  by  quadrant  or  by  the  range  scale  on  the 
carriage. 

With  mortars  this  Case  is  used  exclusively.  It  is  used  with  guns,  (1)  in  fir- 
ing by  battery,  (2)  when  the  position  of  the  target  is  known  but  the  target  is 
not  visible  from  the  gun  on  account  of  smoke,  fog,  etc.,  (3)  in  predicted  firing 
by  piece  when  for  any  reason  direction  cannot  be  accurately  given  by  the 
sight. 

Casemate. — An  obsolete  bombproof  chamber,  usually  of  masonry,  in  which 
cannon  were  placed  to  be  fired  through  embrasures  or  portholes ;  or  one  capable 
of  being  used  as  a  magazine.  See  MINING  CASEMATE. 

Casemate  Battery. — A  storage  battery  in  the  mining  casemate  provided 
as  a  means  of  furnishing  direct  current  for  the  mine  system. 

Casemate  Electrician. — A  specially  qualified  member  of  a  mine  command 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  13 

assigned  to  the  care  and  operation  of  the  mining  casemate.  Insignia:  Red 
mine  case  with  red  bar  below  within  a  yellow  circle,  all  to  be  of  cloth. 

Casemate  Officer. — A  coast  artillery  officer  stationed  at  the  mining  case- 
mate who  controls  its  operation. 

Casernes. — In  a  general  acceptation,  casernes  signify  barracks. 

Cast-iron  Shot. — Projectiles  made  of  cast  iron,  used  in  service  target 
practice. 

Castramentation. — The  art  or  act  of  encamping,  or  the  act  of  marking  or 
laying  out  a  camp. 

Cathead. — A  projecting  piece  of  timber  or  iron  with  a  pulley  at  the  head, 
attached  to  either  side  of  the  bow  of  mine  planters,  by  which  anchors  and 
mine  cases  are  hoisted  or  lowered. 

Center  of  Gravity. — That  point  in  a  body,  or  system  of  bodies  rigidly 
connected,  upon  which  the  body  or  system  will  balance  itself  in  all  positions, 
though  acted  upon  by  gravity. 

Center  of  Gravity  Band. — A  painted  band  one-half  a  caliber  wide  on  gun 
projectiles,  and  six  inches  wide  on  mortar  projectiles.  The  center  of  gravity 
of  the  projectile  is  the  center  of  the  band.  It  also  indicates  where  the  shot 
tongs  are  placed. 

Center  of  Gravity  of  Cannon. — The  center  of  gravity  of  a  cannon  is  near 
the  intersection  of  its  axis  and  the  axis  of  the  trunnions.  The  preponderance 
is  the  excess  or  moment  of  weight  in  rear  of  the  axis  of  the  trunnions  over 
that  of  the  front,  or  the  converse. 

Center  of  Impact. — The  mean  point  of  impact,  or  the  mean  of  all  the 
hits.  When  a  projectile  strikes  the  target  a  number  of  times,  it  is  the  mean 
trajectory. 

Center  Pintle. — A  term  applied  to  a  seacoast  carriage  when  its  axis  of 
rotation  is  approximately  through  the  center,  that  is,  when  it  traverses  about 
a  point  at  its  center. 

Centering  Slope. — The  conical  part  of  the  powder  chamber  between  the 
main  chamber  and  the  forcing  cone. 

Centrifugal  Force. — A  force  whose  direction  is  from  a  center.  For  instance, 
water  is  thrown  from  the  blades  of  a  propeller  from  the  force  issuing  from  its 
center. 

Centrifugal  Fuses. — Firing  devices,  the  action  of  which  depend  upon  cen- 
trifugal force ;  inserted  either  in  the  base  or  point  of  an  armor  or  deck-piercing 
shell  to  ignite  the  bursting  charge. 

Chamber. — See  SHOT  OR  POWDER  CHAMBER. 

Charge. — The  charge  consists  of  the  powder  and  the  projectile.  The  powder 
for  all  large  cannon,  to  include  4.7-inch  guns,  is  enclosed  in  silk  or  serge  bags 
and  is  separate  from  the  projectile.  In  guns  of  greater  caliber  than  six  inches 
it  is  put  up  in  two  or  more  sections  or  bags.  For  smaller  calibers  the  projectile 
and  powder  are  not  separate;  such  ammunition  is  called  "fixed." 

Charts. — See  HARBOR,  DIFFERENCE,  POWTDER,  VESSEL,  BATTLE  AND  SYMBOL 
CHARTS. 

Chase. — The  part  of  a  cannon  in  front  of  the  trunnion  band. 

Chassis. — The  traversing  base  frame  of  a  gun  carriage  upon  which  the  top 
carriage  moves  backward  and  forward. 

Chief  Loader. — A  non-commissioned  officer  in  charge  of  the  loading  of  sub- 


14  THE  SERVICE  OF  COAST  ARTILLERY 

marine  mines.  Insignia:  Red  mine  case  within  a  yellow  circle,  all  to  be  of 
cloth. 

Chief  of  Ammunition  Service. — A  non-commissioned  officer  in  charge  of 
the  magazines,  galleries,  and  service  of  ammunition  for  a  gun  battery,  or  a 
mortar  emplacement. 

Chief  of  Coast  Artillery. — A  general  officer  of  coast  artillery  charged  with 
the  duty  of  keeping  the  War  Department  advised  of  the  efficiency  of  the  coast 
artillery  personnel  and  material,  and  making  such  recommendations  as  will 
tend  to  promote  its  efficiency;  to  confer  with  and  advise  the  chiefs  of  bureaus 
in  all  matters  relating  to  coast  artillery;  to  correspond  direct  with  command- 
ants of  artillery  service  schools  and  the  president  of  the  Artillery  Board  on 
questions  of  a  technical  character  not  involving  matters  of  command,  discipline, 
administration  or  the  status  or  interests  of  individuals;  to  make  recom- 
mendations as  to  the  instruction,  examination,  promotion,  assignment,  special 
duty,  and  transfer  of  coast  artillery  officers  and  men,  as  well  as  methods  and 
courses  for  their  instruction ;  to  issue  direct  to  coast  artillery  officers  bulletins 
and  circulars  on  technical  matters.  He  is  a  member  of  the  General  Staff 
Corps  and  the  Board  of  Ordnance  and  Fortifications. 

Chief  of  Coast  Artillery's  Flag. — See  FLAG  OF  CHIEF  OF  COAST  ARTILLERY. 

Chief  Planter. — A  non-commissioned  officer  in  charge  of  the  service  of  a 
mine  planter.  Insignia:  Red  mine  case  within  a  yellow  circle,  all  to  be  of 
cloth. 

Chronograph. — An  instrument  for  measuring  the  velocity  of  projectiles. 

Chronometer. — An  instrument  for  accurately  measuring  time. 

Circle. — A  plane  figure  bounded  by  a  curved  line,  called  its  circumference, 
which  returns  into  itself,  and  which  is  everywhere  equally  distant  from  a  point 
within  it  called  a  center.  A  circumference  is  divided  into  360  equal  parts, 
each  of  which  is  known  as  a  degree',  each  degree  into  60  parts,  each  of  which 
is  known  as  a  minute ;  each  minute  into  60  parts,  each  of  which  is  known  as  a 
second.  In  the  coast  artillery  service  degrees  are  divided  into  hundredth*,  and 
the  minutes  and  seconds  eliminated. 

Circuit-Closer. — A  device  by  which  submarine  mines  are  fired  electrically 
by  the  vessel  closing  the  circuit. 

Circumference. — See  CIRCLE.  The  circumference  of  any  circle  is  3.1416 
times  the  length  of  its  diameter. 

Cleaner. — An  artilleryman  charged  with  the  care  of  armament  out  of  service. 

Clinometer. — An  instrument  for  measuring  accurately  the  inclination  of  the 
axis  of  the  bore  to  horizontal. 

Clinometer  Rest. — The  support  for  a  clinometer  inserted  in  the  muzzle  of 
the  gun;  it  is  also  called  bore-plug. 

Coast  Artillery  Board. — A  board,  consisting  of  such  number  of  coast 
artillery  officers  as  the  War  Department  may  direct,  to  which  may  be  referred 
from  time  to  time  all  subjects  pertaining  to  the  coast  artillery  upon  which  the 
War  Department  or  the  Chief  of  Coast  Artillery  may  desire  the  board's  opinion 
and  recommendations. 

Coast  Artillery  Company. — An  integral  part  of  the  Coast  Artillery  Corps, 
assigned  to  some  portion  of  the  armament.  The  strength  is  fixed  in  orders; 
the  present  authorized  personnel  of  a  gun  company  of  the  primary  armament 
is,  Captain,  1  First  Lieutenant,  1  Second  Lieutenant,  1  First  Sergeant,  1 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  15 

Quartermaster  Sergeant,  8  sergeants,  12  Corporals,  2  Mechanics,  2  Musicians, 
2  Cooks,  and  81  Privates.  The  number  of  privates  may  be  varied  in  com- 
panies depending  upon  the  armament  to  which  it  is  assigned;  this  is  partic- 
ularly the  case  in  companies  of  the  mine  defense. 

Coast  Artillery  Fort. — The  coast  defenses  at  any  military  post  and  tho 
garrison  assigned  thereto.  Its  command  devolves  upon  the  senior  regular 
coast  artillery  officer  present. 

Coast  Artillery  Garrison. — The  personnel,  to  include  regular  coast  artil- 
lery, coast  artillery  reserves,  and  coast  artillery  supports,  assigned  to  a  coast 
artillery  fort. 

Coast  Artillery  Material. — Coast  artillery  material  is  classified  as  arma- 
ment, range  equipment,  power  and  light  equipment,  and  submarine  defense 
equipment. 

Coast  Artillery  Reserves.— Militia  troops  organized  as  coast  artillery  for 
the  purpose  of  supplementing  the  regular  coast  artillery. 

Coast  Artillery  Supports. — Infantry  or  other  troops  assigned  to  coast 
artillery  forts  to  support  the  artillery  in  repelling  land  attacks  in  the  immediate' 
vicinity  of  the  fortifications. 

Coast  Carriage. — See  CARRIAGE  or  MOUNT. 

Coast  Defense. — The  military  and  naval  dispositions  and  operations  neces- 
sary to  resist  a  naval  attack  on  any  part  of  the  coast  line. 

Coast  Defense  Officer. — A  coast  artillery  officer  assigned  to  duty  on  the 
staff  of  division  or  department  commanders  to  act  in  an  advisory  capacity 
with  respect  to  matters  pertaining  to  the  efficiency  of  coast  artillery  material 
and  to  the  drill,  instruction  and  employment  of  coast  artillery  in  connection 
with  coast  defense  generally. 

Coast  Defense  Ships.— Ships  of  the  monitor  or  gunboat  type,  supple- 
menting the  shore  defenses  at  points  where  the  latter  do  not  give  adequate 
protection,  by  reason  of  the  width  of  the  approaches  or  the  nearness  of  the 
harbor,  city,  or  anchorage,  etc.,  to  the  sea. 

Coast  Guard. — Mobile  troops  placed  at  strategical  points  near  fortified 
portions  of  the  coast  line. 

Collar. — A  device  made  of  wood,  placed  upon  the  chase  of  a  gun  to  make 
the  diameter  equal  to  that  of  the  body  of  the  piece,  to  enable  it  to  be  rolled 
with  facility. 

Colors. — The  silken  national,  and  district  or  regimental  flags  carried  by 
regiments  or  battalions  of  engineers,  troops  comprising  coast  artillery  districts, 
and  regiments  of  infantry.  The  word  is  used  in  contradistinction  to  standards, 
which  are  smaller  in  dimension  and  are  carried  by  regiments  of  cavalry,  and 
regiments  of  field  artillery.  They  are  carried  in  battle,  campaign,  and  on  all 
occasions  of  ceremony  at  district  or  regimental  headquarters  where  two  or  more 
companies  of  the  district  or  regiment  participate. 

Each  coast  artillery  post,  where  two  or  more  companies  of  coast  artillery 
are  stationed,  is  furnished  with  a  service  color,  which  is  the  national  color  made 
of  bunting  or  other  suitable  material,  but  in  all  other  respects  similar  to  the 
silken  national  color.  Garrisons  of  coast  artillery  posts  other  than  district 
headquarters  may  use  them  upon  all  occasions. 

Colors  of  the  Coast  Artillery  Corps. — The  national  color  is  of  silk  5  feet 
6  inches  fly,  4  feet  4  inches  on  the  pike,  which  is  9  feet  long,  including  spear- 


16  THE  SERVICE  OF  COAST  ARTILLERY 

head  and  ferrule;  the  union  is  2  feet  6  inches  long,  with  stars  embroidered  in 
white  silk  on  both  sides  of  the  union;  the  edges  are  trimmed  with  knotted 
fringe  of  yellow  silk  2^  inches  wide;  there  are  two  cords  8  feet  6  inches  long, 
having  tassels,  and  composed  of  red,  white,  and  blue  silk  strands.  The  official 
designation  of  the  artillery  district  is  engraved  on  a  silver  band  placed  on  the 
pike. 

The  corps  color,  of  the  same  dimensions  as  the  national  color,  is  of  scarlet  silk, 
having  embroidered  upon  it  in  colors  the  official  coat  of  arms  of  the  United  States, 
of  suitable  size.  Below  the  coat  of  arms,  in  the  middle,  embroidered  in  yellow 
silk,  are  two  cannon,  crossed;  also  a  scroll  embroidered  in  yellow  silk  and 
bearing  the  inscription,  "U.  S.  Coast  Artillery  Corps,"  embroidered  in  red 
silk;  the  edges  are  trimmed  with  knotted  fringe  of  yellow  silk  1\  inches  wide; 
cord  and  tassels  same  size  as  those  of  the  national  color,  but  of  red  and  yellow 
silk  strands.  Both  sides  of  the  color  are  embroidered  alike. 

One  set  of  national  and  corps  colors  is  issued  to  the  headquarters  of  each 
artillery  district. 

Colors  on  Projectiles. — See  PAINTS  ON  PROJECTILES. 

Combination  Electric  Friction  Primer.— A  primer  combining  the  prin- 
ciples of  friction  and  electric  primers,  the  electric  features  being  modified. 

Combination  Fuse. — A  fuse  inserted  in  the  point  of  shrapnel  which  ignites 
the  bursting  charge  either  upon  impact  or  at  the  completion  of  the  set  time 
interval;  it  contains  both  a  time  and  percussion  fuse,  thus  increasing  the 
chance  of  bursting. 

Commissary  Sergeant. — See  POST  COMMISSARY  SERGEANT. 

Common  Electric  Primer. — A  primer  whose  action  depends  upon  the 
ignition  of  a  small  charge  of  fulminate  fired  by  means  of  a  platinum  bridge 
heated  to  incandescency  by  an  electric  current. 

Common  Friction  Primer. — A  primer  which  operates  solely  by  friction. 

Communication  Officer. — A  coast  artillery  officer  charged  with  the  duty  of 
receiving  and  transmitting  communications  during  drill  or  action. 

The  communication  officer  of  a  battle  command  has  entire  charge  of  the 
system  of  communication,  inspects  the  equipment  of  the  station,  excepting 
the  equipment  pertaining  to  the  searchlight  system,  verifies  the  adjustment  of 
the  position-finding  instruments,  receives  the  report  of  details  and  reports  to 
the  battle  commander  when  the  station  is  in  order,  or  reports  any  defects  that 
he  cannot  immediately  correct.  He  receives  all  orders  from  and  transmits 
all  communications  to  the  district  commander,  and  all  orders  to  and  com- 
munications from  the  fire  and  mine  commanders.  He  sees  that  an  accurate 
record  is  kept  of  all  orders  of  the  battle  commander  and  all  communications  of 
whatever  character  received  at  the  station. 

The  communication  officer  of  a  fire  command  is  in  charge  of  the  station 
under  the  fire  commander.  He  inspects  the  equipment  of  the  station,  verifies 
the  adjustment  of  the  position-finding  instrument,  plotting  board,  etc.  Re- 
ceives the  reports  of  the  battery  commanders  and  transmits  them  to  the  fire 
commander.  He  transmits  the  orders  of  the  fire  commander  to  range  officers, 
or  through  the  latter  to  the  battery  commanders;  receives  all  orders  from  the 
battle  commander,  and  immediately  transmits  same  to  the  fire  commander. 
He  sees  that  an  accurate  record  is  kept  of  all  orders  and  communications  to 
and  from  the  station. 


DEFINITIONS,   ABBREVIATIONS   AND  SIGNS  17 

Communications. — Means  of  transmitting  orders  or  messages  through  the 
tactical  chain  of  artillery  command.  In  the  case  of  mobile  troops  it  includes 
all  routes,  such  as  roads,  railroads,  etc.,  by  which  an  army  communicates  with 
its  base,  or  by  which  several  parts  of  an  army  communicate  with  each 
other. 

Composite  Artillery  Type  Telephone. — A  special  type  of  telephone  pro- 
vided for  permanent  artillery  communications. 

Computer. — A  member  of  the  fire-control  section  who  operates  a  range  or 
deflection  board. 

Concentric. — That  which  has  a  common  center  with  something  else.  A 
stone  thrown  in  a  motionless  pool  of  water  would  cause  concentric  circles  to  form 
on  its  surface. 

Cone  of  Dispersion. — See  ("ONE  OF  SPREAD. 

Cone  of  Spread.— The  imaginary  cone  containing  the  diverging  bullets  or 
fragments  upon  the  explosion  of  a  shrapnel  shell.  This  cone  is  very  long. 

Conical. — Round  and  tapering  to  a  point. 

Console. — A  bracket  whose  projection  is  not  more  than  half  its  height  ;  any 
small  bracket. 

Contact  Firing. — The  electrical  firing  of  a  submarine  mine  when  it  is  struck 
by  an  enemy's  ship. 

Converted  Gun. — A  smooth-bore  gun  in  which  a  tube  containing  rifling 
has  been  inserted. 

Cordage. — Ropes  and  cord  collectively.     See  chapter  on  CORDAGE. 

Cored  Shot. — A  projectile  the  center  of  which  is  partly  hollowed.  It  can 
be  filled  with  a  bursting  charge  and  used  the  same  as  a  shell. 

Corrected  Range. — The  fictitious  range  which  determines  the  elevation  to 
be  given  the  gun,  in  order  to  hit  the  target. 

Corridor  or  Truck  Corridor. — The  elevated  passageway  in  rear  of  the 
traverse  connecting  adjacent  gun  emplacements  at  the  loading  platform  level. 

Corridor  Wall. — The  traverse  wall  along  the  corridor. 

Counter  Attack. — A  counter  attack,  during  an  engagement  of  mobile 
troops,  is  directed  against  the  enemy's  attack,  i.e.,  it  meets  him  before,  or  at 
the  moment  of,  arrival  at  the  defended  position.  The  term  also  applies  to  an 
attack  made  after  a  prior  defensive  attitude  and  directed  against  troops  not 
previously  engaged,  for  example,  in  turning  the  flank  of  an  attacking  force. 
This  is  called  the  decisive  counter  attack,  although,  properly  speaking,  it  is 
the  assumption  of  the  offensive. 

Countermining. — The  operation  of  clearing  a  channel  of  mines,  by  exploding 
large  charges  sufficiently  near  the  mines  to  cause  their  destruction.  The  usual 
method  consists  of  dropping  in  succession  two  or  more  parallel  straight  lines 
of  countermines  at  such  distance  from  each  other  that  their  simultaneous 
explosion  will  destroy  all  mines  within  their  destructive  radius. 

Note. — The  success  of  this  is  very  doubtful,  however,  under  the  present 
mine  system. 

Counter  Recoil. — The  return  of  the  gun  in  battery,  immediately  after  recoil. 

Counterscarp. — Sae  SCARP. 

Counterweight. — The  weight  used  on  disappearing  carriages  to  take  up 
part  of  the  force  of  recoil,  and  to  carry  the  gun  to  the  firing  position.  The 
term  is  also  applied  to  the  weight  on  masking  parapet  mounts. 


18  THE  SERVICE  OF  COAST  ARTILLERY 

Counterweight  Well. — The  pit  in  the  front  end  of  a  gun  platform  for  the 
reception  of  the  counterweight  of  a  disappearing  carriage. 

Cover  Post. — Positions  for  the  members  of  a  mortar  detachment  at  the 
command  "  Take  Cover." 

Cradle. — A  device  employed  for  transporting  heavy  guns  a  short  distance. 

Crane. — A  mechanical  device  for  raising  ammunition  by  means  of  differen- 
tial or  other  blocks. 

Critical  Dimension. — A  term  used  in  connection  with  powder  grains.  It  is 
the  dimension  or  thickness  of  the  web  between  the  perforations  in  a 
multi-perforated  grain.  Also  called  least  dimension.  See  chapter  on  BAL- 
LISTICS. 

Cross  Fire. — Cross  fire  is  where  the  projectiles  from  guns  in  different  posi- 
tions cross  one  another  at  a  particular  point. 

Crow's  Nest. — The  name  commonly  applied  to  the  observing  station  located 
in  the  parapet  or  traverse. 

Cruiser. — A  war  vessel  of  graceful  and  regular  outline.  Armored  Cruisers 
have  a  narrow  beam  as  compared  with  length,  a  high  freeboard,  armor-plated 
turrets  and  belt.  Average  length  about  400  feet,  beam  60  to  70  feet,  draft 
22  to  24  feet,  speed  22  to  24  knots,  displacement  13,000  to  15,000  tons,  armor 
3  to  6  inches  in  thickness,  armament  10-inch,  8-inch,  6-inch,  and  smaller  rapid- 
fire  guns,  and  torpedo  tubes. 

Protected  Cruisers  differ  from  armored  cruisers  in  having  only  protected 
deck  at  water  line.  Average  length  300  to  430  feet,  beam  40  to  50  feet,  draft 
17  to  27  feet,  speed  19  to  23  knots,  displacement  3,000  to  9,000  tons,  armor 
of  deck  \\  to  4  inches,  armament  8-inch,  6-inch,  5-inch,  4-inch,  and  smaller 
rapid-fire  guns,  and  torpedo  tubes. 

Scout  Cruisers  differ  from  other  types  in  having  no  armor  protection.  Aver- 
age speed  22  to  26  knots,  armament  small  rapid-fire  guns. 

Cruiser  Battleship. — A  war  vessel  the  armament  of  which  is  equal  in  powerr 
or  nearly  so,  to  a  battleship,  but  which  cannot  fight  in  a  naval  "battle  line" 
owing  to  the  lightness  of  its  armor  protection.  This  type  of  war  vessel  carries, 
as  its  capital  caliber,  eight  12-inch  guns;  its  armor,  however,  is  only  about  one- 
half  the  thickness  of  that  of  battleships.  This  saving  in  weight  being  given 
to  motive  power,  their  speed  being  about  26  knots.  Their  functions  are  to 
drive  in  or  destroy  the  enemy's  armored  cruisers  and  discover  the  strength 
of  his  battle  front.  They  may  also  be  used  to  harass  the  enemy's  battleships 
either  before  or  during  an  action. 

Crusher  Guage. — A  device  inserted  in  the  mushroom  head  of  the  breech- 
block, or  in  the  bottom  of  the  bore,  to  determine  the  maximum  pressure  of 
the  bore.  Commonly  called  pressure  gauge. 

Curvature  of  the  Earth. — A  term  applied  in  gunnery  to  define  the  amount 
of  bending  of  the  water  surface  of  the  earth  from  the  normal  due  to  the  earth's 
shape.  This  bending  of  the  water  surface  causes  the  target  to  be  on  a  lower 
level  than  that  of  the  gun,  i.e.,  the  apparent  difference  of  level  between  the 
axis  of  the  gun  and  mean  low  water  as  the  position  of  the  target  is  increased 
in  proportion  to  the  range. 

Curve  or  Curved  Line. — A  line  that  changes  direction  at  every  point. 

Curved  Fire. — See  FIRE. 

Cut-off  Jack    Set. — A  form  of  telephone  bridged  on  lines  to  primary  sta- 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  19 

tions  and  booths  to  enable  communication  officers  to  talk  direct  to  any  primary 
station  in  the  fire  command. 

Cylindrical. — Having  the  form  of  a  cylinder;  uniformly  circular. 

Cylindro-Conical. — Having  the  form  of  a  cylinder  the  forward  portion  of 
which  is  conical. 

"D"  Row. — See  HOOPS. 

Danger  Range. — See  DANGER  SPACE. 

Danger  Space. — The  horizontal  distance  within  which  a  target  of  given 
height  would  be  hit  by  a  projectile.  It  is  usually  computed  for  the  standard- 
size  target.  The  danger  space  varies  with  the  range,  the  flatness  of  the  tra- 
jectory, the  height  of  the  target,  and  the  height  of  the  gun  above  the  target. 

Data  Line. — See  INTELLIGENCE  LINE. 

Datum  Point. — A  fixed  point  in  the  field  of  fire  the  true  azimuth  and  range 
of  which  has  been  determined  by  the  Engineer  Corps.  Such  point  or  points 
are  used  in  proving  the  accuracy  of  range  and  position  finding  instruments. 

Deflection. — The  horizontal  angle  between  the  plane  of  sight  and  plane  of 
departure;  it  is  expressed  as  a  reference  number  and  is  set  off  on  the  sight 
deflection  scale. 

Deflection  Board. — A  device  for  determining  the  algebraic  sum  of  the 
deflection  corrections  for  wind,  drift  and  travel  of  target  during  the  time  of 
flight  and  the  predicted  interval.  It  is  used  to  determine  the  reference  numbers 
for  the  deflection  scale  of  the  sight  in  Cases  I  and  II,  and  the  azimuth  correc- 
tion reference  number  in  Case  III;  and,  for  mortars,  the  corrected  azimuth. 

Deflection  Scale. — A  scale  provided  on  sights,  graduated  in  degrees  and 
hundredths  for  the  purpose  of  obtaining  and  applying  corrections  for  deviation. 

Delayed  Automatic  Firing. — A  term  applied  to  one  of  the  three  methods 
of  exploding  submarine  mines,  i.e.,  where  the  apparatus  is  so  arranged  that  the 
mine  is  exploded  when  a  signal  is  given  which  indicates  that  it  has  been  struck. 

Delivery  Table. — The  table  from  which  ammunition  is  delivered  to  the 
truck. 

Density  of  Loading. — The  mean  density  of  the  whole  contents  of  the 
powder  chamber.  It  is  the  ratio  of  the  weight  of  the  powder  charge  to  the 
weight  of  a  volume  of  distilled  water  at  a  temperature  of  39.2  degrees  F.,  which 
would  completely  fill  the  powder  chamber.  The  formula  for  computing  it  is 
A  (density  of  loading)  =  (27. 7W")  /  V,  in  which  W  is  equal  to  the  weight  of  the 
powder  in  pounds  and  V  the  volume  of  the  chamber  in  cubic  inches. 

Department  Artillery  Officer. — See  COAST  DEFENSE  OFFICER. 

Department  Commander. — A  general  officer  assigned  by  order  of  the 
President  to  command  all  the  military  forces  of  the  government  within  the 
limits  of  territorial  divisions  and  departments  which  are  not  excepted  from 
his  control  by  the  War  Department. 

Department  Commander's  Flag. — See  FLAG  OF  DEPARTMENT  COMMANDER. 

Depression  Position-Finder. — A  telescopic  instrument  used  in  the  primary 
and  secondary  stations  of  a  fire-control  base  line,  to  read  either  vertical  or 
horizontal  angles.  When  used  in  the  first  instance  it  is  a  depression-position 
finder,  while  in  the  second  it  is  used  the  same  as  an  ordinary  azimuth  instru- 
ment. Objects  when  viewed  from  an  elevation  appear  under  different  angles 
of  depression  according  to  their  distance  from  the  point  or  points  of  observa- 
tion; this  fact  is  taken  advantage  of  in  the  vertical  base  system  and  is  the 


20  THE  SERVICE  OF  COAST  ARTILLERY 

principle  upon  which  depression-position  range  finders  are  constructed.  The 
depression-position  range  finder  solves,  mechanically,  the  problem  of  determin- 
ing one  side  of  a  vertical  right  triangle,  having  given  a  side  and  two  adjacent 
angles.  The  given,  or  base  side,  is  the  distance  above  sea  level  of  the  axis  about 
which  the  telescope  is  elevated  or  depressed.  The  lower  angle  is  constant  and 
equal  to  90  degrees.  The  depression  angle  varies  with  the  distance  of  the 
observed  target. 

Detonation. — The  practically  instantaneous  combustion  or  decomposition 
of  a  disruptive  explosive  of  high  order. 

Deviation. — Distances  measured  either  in  the  horizontal  plane  at  the  level 
of  the  target  or  in  a  vertical  plane  through  the  center  of  the  target  at  right 
angles  to  the  plane  of  direction.  If  from  the  point  of  impact  of  a  shot  a  per- 
pendicular be  drawn  to  the  plane  of  direction,  the  length  of  this  perpendicular 
is  the  lateral  deviation,  and  it  is  plus  or  minus  according  as  the  point  of 
impact  is  to  the  right  or  left  of  the  line  of  direction  looking  from  the  gun. 
The  distance  from  the  foot  of  this  perpendicular  to  the  center  of  the  target 
is  the  longitudinal  deviation.  It  is  plus  when  the  point  of  impact  is  beyond 
the  tanget  and  minus  when  it  is  short. 

Deviation  at  the  Target. — If  from  the  target  a  line  be  drawn  perpendicular 
to  the  plane  of  direction  intersecting  the  plane  containing  the  line  of  shot,  the 
length  of  this  perpendicular  is  the  "deviation  at  the  target." 

Deviation,  Absolute. — See  ABSOLUTE  DEVIATION. 

Deviation,  Mean  Lateral. — See  MEAN  LATERAL  DEVIATION. 

Deviation,  Mean  Longitudinal. — See  MEAN  LONGITUDINAL  DEVIATION. 

Deviation,  Range. — See  RANGE  DEVIATION. 

Diameter. — A  line  passing  through  the  center  and  terminating  at  both  ends 
in  the  circumference  of  a  circle. 

Difference  Chart. — A  graphic  device  constructed  upon  geometric  principles 
by  which  information  as  to  range  and  azimuth  of  a  target  from  one  point — the 
primary  station — is  converted  mechanically  into  similar  information  with  re- 
spect to  any  other  point,  as  the  directing  gun  or  point  of  a  battery. 

Direct  Fire. — See  FIRE. 

Directing  Gun. — See  DIRECTING  POINT. 

Directing  Point. — A  point  at  or  near  the  battery  for  which  relocation  is 
made  at  the  plotting  room.  It  is  the  point  over  which  the  gun  center  of  the 
plotting  board  is  adjusted.  When  the  pintle  center  of  a  gun  of  a  battery  is 
taken  as  the  directing  point,  such  gun  is  called  the  directing  gun. 

Disappearing  Carriage. — A  gun  carriage  so  constructed  that  it  witl  carry 
its  gun  to  a  firing  position  above  the  parapet  and  upon  discharge  carry  it  back 
to  the  original  loading  position  behind  the  parapet. 

Displacement. — The  horizontal  distance  from  the  vertical  axis  of  the  posi- 
tion finder  of  the  battery  primary  station  to  the  pintle  center  of  the  directing 
gun,  or  some  other  directing  point. 

In  a  marine  sense  the  word  implies  the  quantity  of  water  displaced  by  the 
hull  of  a  ship,  the  weight  of  the  displaced  liquid  being  equal  to  that  of  the 
displacing  body. 

Displacement  of  any  Point. — The  horizontal  distance  in  yards  of  that 
point  from  the  directing  point. 

Distribution  Box. — A  cast-iron  case  through  which  the  cables  of  a  group 


DEFINITIONS/ABBREVIATIONS  AND  SIGNS  21 

of  submarine  mines  are  distributed  from  the  multiple-core  cable  which  runs 
to  the  mining  casemate. 

District  Artillery  Engineer. — A  coast  artillery  officer  charged  with  the 
requisition,  supervision,  maintenance,  inspection  and  accountability  of  the 
signal,  submarine  mine  and  engineer  installations,  property  and  stores  of  an 
artillery  district.  He  inspects  all  such  installations,  property  and  stores  at 
each  post  in  his  district  at  least  once  a  month.  His  tactical  functions  are 
those  of  a  searchlight  officer  of  a  battle  command,  unless  otherwise  assigned 
by  the  district  commander. 

District  Commander. — See  ARTILLERY  DISTRICT  COMMANDER. 

District  Drill. — A  drill  conducted  by  the  district  commander  in  which  all 
the  artillery  elements  of  defense  of  the  district  take  part. 

Ditch. — In  field  fortification,  the  trench  in  front  of  the  parapet,  designed  as  an 
obstacle  to  the  assailant.  It  was  formerly  called  also  a  moat  or  a,  fosse. 

Double  Primary  Station. — A  building  so  constructed  as  to  contain  under 
one  roof  two  primary  stations  with  their  plotting  rooms. 

Double  Secondary  Station. — A  building  so  constructed  as  to  contain  under 
one  roof  two  secondary  stations. 

Drift. — The  divergence  of  the  projectile  from  the  plane  of  departure  due  to 
its  rotation,  its  ballistic  character  and  the  resistance  of  the  air.  It  is  generally 
in  the  direction  of  rotation,  except  for  extreme  elevations  of  high-angle  fire, 
in  which  case  it  may  be  opposite  to  the  original  direction  of  rotation.  For  the 
United  States  service  rifled  guns  it  is  to  the  right.  It  may  be  expressed  either 
in  yards  or  angular  measure. 

Driggs-Schroeder  Rapid-Fire  Gun. — A  rapid-fire  gun  of  2.24-inch  caliber, 
commonly  called  6-pounder.  They  are  distinguished  by  two  models  of  breech 
mechanism,  namely,  screw-block  and  drop-Week. 

Driggs-Seabury  Rapid-Fire  Gun. — A  rapid-fire  gun  of  2.24  and  3-inch 
caliber,  commonly  called  6  and  15-pounders  respectively. 

Drill  Primer. — A  primer  provided  for  reloading,  used  for  drill  purposes. 

Dunnite. — See  EXPLOSIVE  "D." 

Dynamite. — A  detonating  and  disruptive  explosive  of  high  order  used  for 
filling  submarine  mines  and  demolitions  of  all  kinds. 

Earthworks. — In  fortification,  a  general  term  for  all  military  constructions, 
whether  for  attack  or  defense,  in  which  the  material  employed  is  chiefly 
earth. 

Ecrasite. — A  high  explosive  compound  of  foreign  manufacture. 

Eight-inch  Gun. — A  seacoast  cannon  usually  40  calibers  long  and  of  8-inch 
caliber. 

Elasticity. — That  property  by  which  bodies  recover  their  former  shape  and 
volume  after  having  yielded  to  some  force.  Elasticity  of  steel  permits  its 
extension  to  a  certain  limit,  beyond  which  a  permanent  set  would  take  place. 
This  limit  is  known  as  the  limit  of  elasticity. 

Electric  Ballistic  Machine. — See  CHRONOGRAPH. 

Electric  Firer. — See  EXPLODER. 

Electric  Mines. — Submarine  mines  fired  by  electric  current;  they  are  of 
two  classes,  controllable  and  non-controllable. 

Electric  Primer. — See  COMMON  ELECTRIC  PRIMER. 

Electrician  Detachment. — A  detachment  consisting  of  the  electrician  ser- 


22  THE  SERVICE  OF  COAST  ARTILLERY 

geants  and  necessary  assistants  detailed  from  the  enlisted  personnel,  charged 
with  the  care  and  preservation  of  the  electrical  installations,  etc.,  of  a  fort. 

Electrician  Sergeant. — A  non-commissioned  staff  officer.  Electrician  ser- 
geants are  of  two  classes.  The  first  class  are  charged  with  the  immediate 
supervision,  care,  and  operation  of  a  division  of  the  electrical  installations, 
including  searchlights  and  power  plants  when  necessary,  in  addition  to  the 
duties  prescribed  for  electrician  sergeants,  second  class.  Any  duty  in  con- 
nection with  the  electrical  installations,  including  the  mechanical  work  of 
repairing  electrical  apparatus  and  the  care  and  operation  of  searchlights. 
The  second  class  are  charged  specifically  with  the  care,  repair  and  maintenance 
of  the  electrical  installations,  including  lines  and  means  of  communication,  as 
well  as  any  duty  in  connection  with  the  electrical  installations,  including 
mechanical  work  necessary  in  repairing  the  electrical  apparatus,  and  the  care 
and  operations  of  searchlights  and  small  power  plants.  Insignia :  First  Class. 
Gold  wreath  with  a  white  forked  lightning  within  and  a  small  red  bar  about 
three-quarters  of  an  inch  long  between  the  lightning  and  the  wreath,  all  below 
a  sergeant's  chevrons.  The  lightning,  bar,  and  wreath  to  be  of  silk  embroidery 
thread.  Second  Class.  Same  as  first  class,  omitting  the  small  bar. 

Elevation. — A  general  term  used  to  denote  the  inclination  in  a  vertical 
plane  given  to  the  axis  of  the'gun  in  pointing.  See  SIGHT  ELEVATION,  QUAD- 
P.ANT  ELEVATION. 

Elevation  Setter. — The  member  of  a  mortar  detachment  who  lays  the  mor- 
tar in  elevation. 

Elliptical. — Oblong  with  rounded  ends. 

Elongated  Projectiles. — The  modern  type  of  coast  artillery  projectiles. 

Emergency  Position  Finder. — A  self-contained  horizontal  position  finder, 
or  a  d  pression  position  finder  constructed  for  use  on  low  sights  and  suffi- 
ciently accurate  for  emergency  purposes.  It  is  operated  from  the  observing 
station  (crow's  nest)  at  a  battery  in  case  the  regular  instrument  or  station  is 
destroyed. 

Emergency  Station. — A  range-finding  station  provided  for  use  in  case  a 
regular  station  of  a  permanent  base  line  has  been  destroyed.  These  stations 
are  so  located  that  they  can  be  used  to  replace  the  primary  or  secondary  station 
of  one  or  more  base  lines.  The  term  is  also  applied  to  the  observing  station  at 
the  battery,  where  an  emergency  depression  position-finder  is  mounted. 

Emergency  System. — A  system  of  position-finding,  used  in  an  emergency. 
It  employs  a  self-contained  position-finder  located  at  the  battery,  with  or 
without  a  plotting  board. 

Emplacement. — That  part  of  a  battery  pertaining  to  the  position,  protection 
and  service  of  one  gun  or  mortar,  or  a  group  of  mortars. 

Emplacement  Book. — See  BATTERY  EMPLACEMENT  BOOK. 

Emplacement  Officer. — A  coast  artillery  officer  in  immediate  charge  of  the 
emplacements  of  a  gun  battery  or  one  pit  of  a  mortar  battery.  He  is  the  bat- 
tery commander's  assistant  at  the  guns  to  which  he  is  assigned.  He  is  respon- 
sible to  the  battery  commander  for  the  condition  of  the  emplacement  and 
material,  as  well  as  for  the  efficiency  of  its  service.  Upon  arrival  at  the'  em- 
placement before  a  drill,  practice  or  action,  he  makes  a  careful  inspection  of  all 
parts  of  the  guns  and  carriages,  the  equipment  and  implements  to  be  used, 
giving  special  attention  to  the  elevating  and  traversing  devices  as  well  as  those 


DEFINITIONS.  ABBREVIATIONS  AND  SIGNS  23 

for  running  the  piece  in  and  from  battery;  recoil  cylinders — to  see  that  they 
arc  properly  filled  with  the  right  amount  and  kind  of  oil,  and  that  the  plugs 
are  properly  inserted;  obturators — to  see  that  they  are  properly  adjusted; 
pads — in  serviceable  condition.  In  case  of  firing — to  see  that  the  throttling 
and  buffer  valves  are  properly  set  and  locked;  to  see  that  the  motor  generator, 
motors  and  controllers,  firing  attachments,  firing  batteries  and  circuits  are  in 
order;  that  the  sights,  subscales  of  azimuth  circles  are  in  adjustment;  that 
sponges  and  rammers  are  of  proper  kind  and  gauge  and  in  serviceable  con- 
dition; that  suitable  vessels  are  provided  for  the  water  necessary  for  sponging 
out  the  bore;  that  all  necessary  charts  are  on  hand;  and  that  ammunition 
hoists  are  in  working  order. 

As  the  efficiency  of  a  battery  depends  primarily  on  the  correctness  of  ad- 
justment of  each  of  the  devices  mentioned  above,  the  necessity  of  a  thorough 
inspection  can  not  be  too  strongly  recommended. 

Emplacement  officers  of  mortar  batteries  are  charged  with  the  corresponding 
duties  in  so  far  as  they  pertain  to  a  mortar  battery. 

Endurance  of  Cannon. — The  life  of  a  cannon  or  the  number  of  times  a 
piece  is  capable  of  being  fired  before  relining  is  necessary.  In  the  case  of 
heavy  guns  their  life  is  assumed  to  be  approximately  250  service  shots. 

Energy  of  the  Projectile. — The  energy  stored  up  in  the  projectile  by  the 
force  of  expanding  powder  gases  generated  by  the  explosion  of  the  charge. 
It  is  expressed  usually  in  foot-tons.  When  a  projectile  is  in  motion  it  is  said 
to  have  energy,  i.e.,  it  is  capable  of  doing  work  and  overcoming  resistance. 
The  formula  for  computing  it  is:  E  =  Wv2 1 (4480y) ,  in  which  W  is  the  weight 
of  the  projectile  in  pounds,  v  is  velocity  in  feet  per  second,  and  g  the  accelera- 
tion due  to  gravity  (mean  value  32.16). 

Energy  of  Recoil. — An  expression  denoting  the  work  done  in  recoil  of  a 
gun  when  fired.  The  recoil  may  be  reduced  by  decreasing  the  weight  of  the 
projectile,  decreasing  the  muzzle  velocity,  or  by  increasing  the  weight  of  the 
gun. 

Enfilade  Fire. — Fire  which  rakes  a  fighting  line,  the  gun  being  on  the 
prolongation  of  the  line.  In  naval  or  fortress  engagements  fire  delivered  on 
the  stern  or  bow  of  a  ship  so  that  the  projectiles  rake  the  whole  length  of  the 
deck. 

Engineer. — A  non-commissioned  staff  officer  whose  duty  it  is  to  supervise, 
care  for,  and  operate  the  power  plants,  machine  and  repair  shops,  and  such 
mechanical  and  electrical  apparatus  used  for  power  purposes  as  may  be  placed 
under  his  charge.  He  may  be  required  to  perform  such  other  technical  duties 
as  may  be  necessary  in  the  district  or  at  the  post  to  which  assigned.  Insignia : 
Gold  wreath  with  a  red  governor  within  and  a  small  white  star  about  one-half 
of  an  inch  above  the  governor,  all  to  be  of  embroidery  thread. 

Equalizing  Pipe. — A  pipe  connecting  corresponding  ends  of  two  recoil 
cylinders  for  the  purpose  of  equalizing  the  pressure  therein. 

Erosion  of  the  Bore. — The  wearing  away  of  the  rifling  of  the  bore. 

Estuary. — A  passage,  as  at  the  mouth  of  a  river  or  lake  where  the  tide 
meets  the  current ;  an  arm  of  the  sea. 

Exploder.— An  electrical  machine  operated  by  hand,  used  to  fire  electric 
fuses  and  primers. 

Explosive. — A  substance  or  a  mixture  of  substances  which,  when  heated, 


24  THE  SERVICE  OF  COAST  ARTILLERY 

• 

struck,  or  subjected  to  the  shock  of  another  explosive  results  in  the  rapid 
formation  of  a  great  volume  of  highly  heated  gas. 

Explosive  Compound. — An  explosive  whose  ingredients  are  united  chem- 
ically. Nitro-glycerine  and  guncotton  are  explosive  compounds. 

Explosive  "D,"  or  Dunnite. — A  shell  filler  the  exact  ingredients  of  which 
are  secret.  It  is  a  high  explosive  compound.  It  is  not  fusible  and  shells  are 
filled  by  compression.  It  is  the  least  sensitive  to  shock  of  all  the  explosives 
used  in  the  service. 

Explosive  House. — A  structure  in  which  high  explosives  are  stored  on  a 
military  post;  frequently  referred  to  as  a  magazine.  Authorities  do  not  agree 
as  to  the  most  suitable  type.  Some  advocate  light  wooden  structures,  the 
debris  of  which  in  case  of  explosion  would  be  thrown  a  comparatively  short 
distance;  others  recommend  a  building  of  corrugated  iron  with  asphaltum 
floors,  making  the  house  fireproof.  Structures  of  this  characte:  are  usually 
protected  by  earthworks. 

Explosive  Mixture. — An  explosive  whose  ingredients  are  mixed  mechanic- 
ally. Gunpowder  is  an  explosive  mixture. 

Exterior  Crest. — The  line  of  intersection  of  the  superior  and  exterior  slopes. 

Exterior  Slope. — The  outer  slope  of  the  parapet  of  a  battery. 

Extreme  Range. — The  greatest  accurate  range  obtained  by  a  projectile  in 
its  flight.  For  example,  the  extreme  range  of  the  16-inch  breech-loading  rifle, 
model  1895,  is  approximately  21  miles.  The  extreme  range  against  armor  for 
the  12-inch  breech-loading  rifle,  model  1900,  is  approximately  13,000  yards,  or 
1\  miles. 

Face  of  the  Breech. — The  rear  terminal  plane  of  the  gun  perpendicular  to 
the  axis  of  the  bore.  • 

Face  of  the  Muzzle. — The  front  terminal  plane  of  the  gun  perpendicular 
to  the  axis  of  the  bore. 

Faces  of  the  Rimbases. — The  end  planes  of  the  rimbases  perpendicular  to 
the  axis  of  the  trunnions. 

Faces  of  the  Trunnions. — The  end  planes  of  the  trunnions  perpendicular 
to  their  axis. 

Field  of  Fire. — The  designation  of  the  area  covered  by  certain  armament, 
for  example,  that  of  a  battery. 

Fifteen-Pounder. — Term  applied  to  a  3-inch  rapid-fire  gun.  It  denotes 
the  proper  weight  of  projectile  for  the  piece. 

Fillet. — That  portion  of  metal,  filling  the  re-entrant  angle  formed  by  two 
surfaces  not  tangent,  thus  avoiding  a  sharp  corner.  The  term  is  also  applied 
to  the  metal  cut  away  in  removing  the  sharp  edge  formed  by  the  intersection 
of  two  surfaces. 

Final  Velocity. — See  REMAINING  VELOCITY. 

Fire. — The  discharge  of  firearms  and  the  destruction  caused  by  their  pro- 
jectiles. Artillery  fire  is  classified  as  direct,  curved  and  high-angle  fire.  Direct 
fire  is  fire  with  high  velocities  and  angles  of  elevation  not  exceeding  fifteen 
degrees.  Curved  fire  is  fire  with  low  velocities  and  angles  of  elevation  not  less 
than  fifteen  degrees.  High  angle  fire  is  fire  with  low  velocities  and  angles  of 
elevation  not  less  than  forty-five  degrees.  See  ORDERS  OF  FIRE;  ENFILADE 
FIRE;  FLANKING  FIRE;  FRONTAL  FIRE;  OBLIQUE  FIRE;  REVERSE  FIRE. 

Fire  Area. — The  area  covered  by  the  armament  of  a  fire  command. 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  25 

Fire  Command. — A  fire  command  consists  normally  of  four  batteries  of 
two  guns  each,  or  in  the  case  of  a  mortar  fire  command,  of  two  mortar  bat- 
teries consisting  of  two  pits  each.  The  batteries  of  a  fire  command  should  be 
so  located  that  their  fire  covers  the  same  or  adjoining  water  areas,  and  so 
located  that  the  artillery  fire  therein  will  not  interfere  with  that  of  any  other 
fire  command. 

The  armament  of  an  artillery  fort  or  post  may  be  divided  into  two  or  more 
fire  commands. 

Fire  Commander. — A  coast  artillery  officer  assigned  in  orders  from  district 
headquarters  to  command  a  fire  command. 

A  fire  commander  is  responsible  to  the  battle  commander  for  the  tactical 
efficiency  of  his  command.  He  is  in  direct  communication  with  his  battle 
commander  and  each  battery  commander  in  his  command. 

He  is  both  an  administrative  and  tactical  commander;  his  administrative 
duties,  however,  are  confined  to  those  affecting  the  tactical  efficiency  of  the 
fire  command.  In  general  he  exercises  his  administrative  duties  verbally  or 
informally.  Generally  orders  to  his  fire  command  are  issued  from  post  head- 
quarters. All  communications  to  and  from  post  headquarters  affecting  his  fire 
command  are  referred  to  him  for  his  information  and  remark.  His  office  is  not 
one  of  record;  he  consults  the  records  at  post  headquarters  for  any  needed 
information. 

On  battery  drill  days  he  visits  the  batteries  of  his  command  during  drill, 
and  on  days  of  indoor  instruction  visits  the  companies  during  instruction 
hours.  He  supervises  battery  target  practice. 

He  requires  a  thorough  knowledge  of  the  installation,  equipment  and  system 
of  fire  control  and  drill  on  the  part  of  the  officers  of  his  command,  and  en- 
courages and  recommends  improvements  in  drill  or  material. 

He  should  keep  himself  constantly  informed  as  to  the  condition  of  the 
material  of  each  battery  in  his  command  as  well  as  to  the  efficiency  of  all  sup- 
plies. 

In  battle  command  drill  or  in  action,  he  takes  up  promptly  the  attack  of 
the  targets  assigned  or  indicated  by  the  command  of  the  battle  commander. 
When  ordered  to  assume  the  exercise  of  independent  fire  action,  he  fights  his 
batteries  in  accordance  with  his  own  judgment.  He  is  authorized  by  regula- 
tions to  order  independent  battery  action  whenever,  in  his  opinion,  the  con- 
dition of  the  naval  attack  renders  such  action  advisable,  provided  independent 
fire  command  action  has  been  ordered,  or  urgency  renders  it  necessary.  He 
uses  his  own  judgment  as  to  orders  of  fire  and  rate  of  fire,  unless  these  have 
previously  been  prescribed  by  the  battle  commander. 

At  night  the  illuminating  light  assigned  to  his  fire  area  is  under  his  immedi- 
ate control. 

Fire  Commander's  Station. — A  station  overlooking  a  fire  area  occupied  by 
the  fire  commander  and  necessary  assistants  during  drill  or  action. 

Fire  Control. — The  exercise  of  those  tactical  functions  which  determine: 
(a)  The  objective  of  fire.  (6)  The  volume  and  concentration  of  fire,  (c)  The 
accuracy  of  fire. 

The  term  /ire-control  system  includes  the  means  employed  in  fire-control, 
the  scheme  of  its  installation  and  method  of  its  use.  The  material  as  installed, 
which  is  employed  in  the  fire-control  of  a  battery  or  district,  is  called  the  fire- 


26  THE  SERVICE  OF  COAST  ARTILLERY 

control  installation  for  that  battery  or  district.     Installations  are  either  standard 
or  provisional. 

Fire-control  material  may  be  classified  under  the  following  heads: 

a.  Instruments  for  the  observation  and  location  of  targets. 

b.  Instruments  for  the  determination  of  firing  data. 

The  personnel  employed  in  fire  control  is  called  the  fire-control  personnel. 

Fire-Control  Installation. — See  FIRE  CONTROL. 

Fire-Control  System. — See  FIRE  CONTROL. 

Fire  Left. — When  marked  on  the  deflection  scales  of  telescopic  sights 
indicates  minus  deflection  (muzzle  pointed  left). 

Fire  Right. — When  marked  on  the  deflection  scales  of  telescopic  sights 
indicates  plus  correction  (muzzle  pointed  right). 

Fired  Standard  Primer. — See  DRILL  PRIMER. 

Fireman. — A  non-commissioned  staff  officer  charged  with  such  duties  as 
pertain  to  the  care  and  operation  of  boilers  and  accessories,  including  the  police 
of  the  boiler  and  engine  room.  He  may  be  required  to  assist  the  engineer  in 
his  work.  Insignia:  A  bar  and  an  arc  of  one  bar  of  red  cloth  inclosing  a  red 
governor  made  of  yellow  cloth. 

Firing  Interval. — The  interval  of  time  between  consecutive  shots  of  the 
same  gun  or  mortar  in  continuous  firing. 

Firing  Machine  or  Electric  Firer. — See  EXPLODER. 

Five-Inch  Gun. — A  rapid-fire  gun  usually  45  to  50  calibers  long  and  of 
5-inch  caliber.  Made  by  the  Ordnance  Department. 

Fixed  Ammunition. — When  the  cartridge  case  is  attached  to  the  projectile, 
the  two  together  are  called  fixed  ammunition.  It  is  not  used  in  large  calibered 
guns  on  account  of  the  disadvantage  of  handling  and  the  difficulty  of  arranging 
and  preserving. 

Fixed  Armament. — Guns  and  mortars  of  various  sizes  and  powers,  mounted 
on  stationary  carriages. 

Fixed  Defenses. — Defensive  works  ashore  within  the  line  of  defense. 
'  Fixed   Mount. — A  mount  or  carriage  provided  for  guns  and  mortars  in 
permanent  works  and  not  designed  to  be  moved  from  place  to  place. 

Fixed  Light. — A  searchlight  intended  to  demarcate  the  outer  limit  of  a 
battle  area  and  illuminate  any  vessel  entering  it. 

Flag  of  Admiral  of  the  Navy. — A  flag  consisting  of  four  white  stars,  on 
a  blue  field  of  bunting,  placed  at  the  corners  of  an  imaginary  square,  whose 
diagonals  are  horizontal  and  vertical. 

Flag  of  Artillery  District  Commander. — A  flag  of  scarlet  bunting,  rectan- 
gular in  shape,  1-foot  6-inch  hoist  and  2-foot  fly  for  small  boats  and  launches, 
and  2-foot  3-inch  hoist  and  3-foot  fly  for  large  boats.  In  the  center  of  both 
sides,  crossed  cannon  in  yellow,  with  a  medallion  at  their  intersection,  in  scarlet, 
having  an  oblong  projectile  in  yellow.  The  truck  of  the  staff  to  be  a  gilt  ball. 

Flag  of  Assistant  Secretary  of  the  Navy. — The  same  as  that  for  Secre- 
tary of  the  Navy,  except  the  anchor  and  stars  are  blue  on  a  white  field  of  bunting. 

Flag  of  Assistant  Secretary  of  War. — The  same  as  that  for  Secretary  of 
War,  except  the  stars  are  scarlet  on  a  white  field  of  bunting. 

Flag  of  Chief  of  Coast  Artillery. — A  flag  of  scarlet  bunting,  rectangular 
in  shape,  3-foot  hoist  and  4-foot  9-inch  fly.  The  rank  to  be  indicated  by  a 
white  star  (or  stars  of  appropriate  number  if  above  the  rank  of  brigadier  general) 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  27 

of  suitable  size  placed  in  the  center  line  of  the  length  of  the  flag.     The  truck 
of  the  staff  to  be  a  gilt  ball. 

Flag  of  Department  Commander. — Same  as  that  of  Chief  of  Coast  Artil- 
lery, with  rank  indicated  by  appropriate  number  of  stars. 

Flag  of  Post  Commander  (Coast  Artillery). — A  pennant  of  bunting,  tri- 
angular in  shape,  1-foot  hoist  and  3-foot  fly;  the  third  nearest  the  staff  to  be 
a  blue  field  bearing  thirteen  stars  and  the  remaining  two-thirds  to  be  scarlet. 
The  truck  of  the  staff  to  be  a  gilt  ball  for  post  commanders  above  the  rank  of 
captain,  and  for  post  commanders  of  a  lower  grade  to  be  flat. 

Flag  of  President  of  the  United  States. — A  flag  consisting  of  the  official 
coat  of  arms  of  the  United  States,  of  suitable  size,  in  the  center  of  a  blue  field 
of  bunting. 

Flag  of  Rear  Admiral  of  the  Navy. — A  flag  consisting  of  two  stars,  on  a 
blue  field  of  bunting,  symmetrically  placed  on  a  vertical  line  in  the  center  of 
the  flag. 

Flag  of  the  Secretary  of  the  Navy.  — A  flag  consisting  of  four  white  stars, 
on  a  blue  field  of  bunting,  symmetrically  placed  in  the  four  corners,  surrounding 
a  vertical  white  anchor. 

Flag  of  the  Secretary  of  War. — A  flag  consisting  of  four  white  stars,  on  a 
scarlet  field  of  bunting,  surrounding  the  official  coat  of  arms  of  the  United 
States. 

Flag  of  the  United  States. — A  flag  with  thirteen  horizontal  stripes,  seven 
red  and  six  white,  the  red  and  white  stripes  alternating;  the  union  of  the  flag 
consists  of  white  stars  in  a  blue  field  placed  in  the  upper  quarter  next  the  staff, 
and  extending  to  the  lower  edge  of  the  fourth  red  stripe  from  the  top,  the 
length  of  the  union  being  13/32  of  the  full  length  of  the  flag;  the  number  of 
stars  is  the  same  as  the  number  of  States  in  the  Union. 

Flag  of  Vice  Admiral  of  the  Navy. — A  flag  consisting  of  three  stars,  on  a 
blue  field  of  bunting,  placed  at  the  vertices  of  an  imaginary  isosceles  triangle, 
whose  base  is  horizontal. 

Flags. — See  BATTLE  FLAG,  COLORS,  COLORS  OF  COAST  ARTILLERY  CORPS, 
GARRISON  FLAG,  POST  FLAG,  STORM  FLAG,  SUBMARINE  BOAT  SIGNAL  FLAG. 

Flagship.— The  vessel  which  carries  the  commanding  officer  of  a  fleet  or 
squadron.  It  is  distinguished  by  the  flag  of  the  officer  in  command,  flying  at 
the  main  mast. 

Flanking  Fire. — Fire  directed  along  the  front  of  or  nearly  parallel  to  the 
enemy's  line. 

Floating  Defenses. — Vessels  used  for  defensive  purposes,  including  monitors, 
gunboats,  scout  ships,  torpedo  boats,  submarine  boats,  patrol  and  picket  boats. 

Foot-Ton. — The  energy  expended  or  necessary  to  raise  a  weight  equal  to  a 
long  ton,  or  2,240  pounds,  one  foot. 

Forcing. — As  applied  to  a  projectile,  forcing  is  the  operation  by  which  a 
projectile  is  made  to  take  hold  of  the  grooves  of  the  bore. 

Forcing  Cone. — The  part  of  the  bore  of  a  gun  immediately  in  front  of  the 
centering  slope.  It  is  formed  by  cutting  away  the  lands  so  as  to  decrease  their 
height  uniformly  from  front  to  rear. 

Fort  Commander. — See  COAST  ARTILLERY  FORT. 

Fort  Record  Book. — A  permanent  confidential  record  book  containing  the 
history  of  the  works,  their  object,  armament,  scheme  of  defense,  and  all  infor- 


28  THE  SERVICE  OF  COAST  ARTILLERY 

mation  of  value  regarding  the  equipment  and  installation.  It  is  supplemented 
by  the  Fort  Record  Book  Files,  in  which  copies  of  all  confidential  papers  and 
maps  are  kept. 

Fortified  Point. — A  general  term  indicating  a  city,  harbor,  anchorage, 
estuary,  or  any  limited  portion  of  the  coast  line  that  is  defended  by  fixed 
defenses. 

Fosse. — See  DITCH. 

Four-Inch  Rapid-Fire  Gun. — A  seacoast  cannon,  usually  40  calibers  long 
and  of  4-inch  caliber. 

Friction. — A  force  acting  between  two  bodies  at  their  surface  of  contact, 
so  as  to  resist  their  sliding  on  each  other.  Friction  is  of  three  kinds;  sliding 
and  rolling  friction,  which  act  with  solids ;  and  fluid  friction,  which  acts  with 
liquids  and  gases. 

Friction  Primer. — See  COMMON  FRICTION  PRIMER. 

From  Battery. — The  position  of  a  gun  when  withdrawn  from  its  firing 
position. 

Front  Pintle. — A  term  applied  to  a  coast  carriage  where  its  axis  of  rotation 
is  at  or  near  its  front  end,  i.e.,  where  it  traverses  about  a  point  in  front  of 
its  center. 

Frontal  Fire. — Fire  which  is  directed  perpendicularly,  or  nearly  so,  to  the 
objects  fired  at. 

Frustum. — That  part  of  a  solid  next  to  a  base  formed  by  cutting  oft7  the  top. 

Fulcrum. — A  means  of  support  for  a  lever  about  which  it  turns  in  lifting  or 
moving  a  body. 

Fulminate. — A  very  sensitive  explosive  compound  used  in  fuses,  primers 
and  caps. 

Fuse. — A  mechanical  firing  device  used  for  exploding  a  bursting  charge. 
See  chapter  on  FUSES  AND  PRIMERS. 

Gabion. — A  wicker  cylinder  of  strong  basket-work  open  at  both  ends.  Its 
usual  dimensions  are  2  feet  in  diameter  and  2|  feet  in  height.  They  are  filled 
with  earth  and  used  for  defensive  purposes  in  field  fortification. 

Gallery. — Any  passage  covered  over  head  and  at  the  sides. 

Galvanometer. — An  instrument  used  for  detecting  the  existence,  and  de- 
termining the  strength  and  direction  of  an  electric  current. 

Garrison  Flag.— The  national  flag,  36  feet  fly  and  20  feet  hoist.  Hoisted 
only  on  holidays,  important  occasions  and  during  engagements.  In  the  latter 
case  it  is  called  the  battle  flag. 

Garrison  Gin. — A  lifting  tackle  used  in  mechanical  maneuvers  of  coast 
artillery  armament.' 

Gas  Check. — The  essential  mechanical  feature  of  an  obturator  which  enables 
it  to  prevent  the  escape  of  gas. 

Gas  Check  Pad. — A  pad  made  of  asbestos  and  tallow  enclosed  in  a  canvas 
cover  and  compressed  under  heavy  pressure.  Under  the  weight  of  firing  the 
plastic  nature  of  the  pad  causes  it  to  press  outward  against  the  gas  check  seat 
and  inward  against  the  spindle,  forcing  the  split  rings  firmly  in  their  seats  and 
completely  stopping  the  passage  to  the  escape  of  gas. 

Gear  Wheel  (or  Cog  Wheel). — A  wheel  with  teeth  on  the  circumference  to 
mesh  with  a  rack,  worm  ring,  or  another  gear  wheel. 

General  Defense  Plan. — The  scheme  of  defense  formulated  prior  to  an  at- 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  29 

tack.  A  variety  of  these  plans,  based  on  the  character  of  attack  to  be  expected, 
should  be  prepared  and  issued  to  the  command. 

Glacis. — In  field  fortification  a  mound  of  earth  which  inclines  from  the 
front  of  the  ditch  toward  the  foreground,  thus  forcing  the  assailant  to  full 
exposure  to  the  fire  from  the  parapet  before  reaching  the  ditch. 

Gravimetric  Density. — A  term  which  refers  to  the  ratio  of  the  weight  of  a 
unit  volume  of  a  standard  powder  to  the  weight  of  the  same  volume  of  any 
other  powder,  i.e.,  the  gravimetric  density  of  a  powder  is  the  weight  in  pounds 
of  a  volume  of  27.68  cubic  inches  of  the  powder  not  pressed  together  by  its  own 
weight.  (27.68  is  the  number  of  cubic  inches  occupied  by  one  pound  of  water). 

Gravity. — That  force  which  tends  to  draw  all  bodies  toward  the  earth  with 
uniformly  increasing  velocity.  Its  mean  value  equals  32.16  foot-seconds.  An 
example  of  gravity  may  be  demonstrated  as  follows:  A  projectile  thrown 
from  a  mortar  at,  say,  an  angle  of  90  degrees,  would  travel  upward  until  the 
propelling  force  under  or  behind  it  ceased  to  exist,  it  would  then  take  a  down- 
ward course — drawn  by  gravity — and  strike  the  surface  at  a  velocity  equal  to 
the  original  initial  velocity  which  it  had  on  leaving  the  muzzle. 

Graze. — The  point  at  which  a  projectile  strikes  a  surface  and  rebounds 
onward. 

Grooves. — In  ordnance,  the  spiral  hollow  cuts  made  in  the  surface  of  the 
bore. 

Guard  Room. — A  room  in  the  battery,  or  guard  house,  set  aside  for  the  use 
of  the  guard. 

Gun. — A  term  applied  in  its  most  general  application  to  any  weapon  which 
throws  or  propels  a  missile  to  a  distance ;  any  firearm  or  instrument  for  throwing 
projectiles  by  the  expanding  force  of  powder  gas,  consisting  of  a  tube  or  barrel 
closed  at  one  end.  In  a  restricted  sense,  the  term  is  applied  to  that  class  of 
cannon  in  which  the  length  of  bore  is  great  in  comparison  with  the  caliber. 

Gunboat. — Any  boat  of  light  draft  carrying  one  or  more  guns.  They 
usually  resemble  cruisers,  but  are  much  smaller.  Speed  less  than  14  knots, 
displacement  2,000  tons  or  less.  Armament,  6-inch,  5-inch,  4-inch  and  smaller 
rapid-fire  guns. 

Gun  Carriage. — See  CARRIAGE  or  MOUNT. 

Gun  Commander. — A  specially  qualified  non-commissioned  officer  in  direct 
charge  of  a  gun  section.  When  assigned  in  command  of  mortar  pits  they  are 
called  pit  commanders]  to  ammunition  sections,  chiefs  of  ammunition  service. 

Gun  Commander's  Range  Scale. — See  RANGE  SCALE. 

Gun  Company. — A  company  assigned  to  the  service  of  direct-fire  guns  only. 

Gun  Cotton. — A  detonating  and  disruptive  explosive  of  high  order  made 
of  unspun  cotton  waste,  used  in  shells,  torpedoes  and  for  demolitions  of  all 
kinds. 

Gun  Differences. — Differences  in  range  and  azimuth  to  the  target  from  the 
gun  and  from  the  directing  point,  due  to  gun  displacement. 

Gun  Displacement. — The  horizontal  distance  in  yards  from  the  vertical 
axis  of  the  directing  gun  to  the  pintle  center  of  any  other  gun  of  the  battery, 
or  from  the  directing  point  to  the  pintle  center  of  any  gun  of  the  battery. 

Gun  Lift. — See  CARRIAGE  or  MOUNT. 

Gun  Platform. — That  part  of  a  battery  upon  which  the  gun  carriage  rests. 

Gun  Pointer. — A  specially  qualified  member  of  a  gun  section  charged  with 


30  THE  SERVICE  OF  COAST  ARTILLERY 

the  proper  aiming  or  laying  of  a  gun,  or  the  chief  of  a  mortar  detachment  who 
supervises  the  loading  and  laying  of  a  mortar.  Insignia :  Red  crossed  cannon 
within  a  yellow  circle,  all  to  be  of  cloth. 

Gun  Section. — A  detail  of  the  enlisted  personnel,  consisting  of  a  gun  com- 
mander, a  gun  detachment,  ammunition  detachment  and  reserve.  There  is  one 
gun  section  for  each  piece  assigned  to  a  battery  of  the  primary  armament  for 
service  or  drill ;  for  batteries  of  the  secondary  armament,  the  detachment  for 
all  of  the  pieces  constitutes  one  gun  section  under  a  single  gun  commander. 

Gunner. — A  specially  qualified  enlisted  man  who  has  passed  the  examination 
in  elementary  gunnery.  They  are  classified  as  first-  and  second-class  gunners. 
Insignia:  First  Class.  In  gun  or  mortar  company;  red  projectile,  with  red 
bar  below.  In  mine  company;  red  mine  case,  with  red  bar  below.  Second 
Class.  Same  as  first  class,  omitting  the  bar.  All  to  be  of  cloth. 

Gunner's  Quadrant. — An  instrument  usually  used  in  laying  mortars  to  give 
quadrant  elevation  by  either  applying  it  at  the  breech  or  muzzle. 

Gunnery. — That  branch  of  military  science  which  comprehends  the  theory 
of  projectiles,  and  the  manner  of  constructing  and  using  ordinance.  See 
BALLISTICS. 

Gunnery  Specialists. — Specially  qualified  enlisted  men,  such  as  Master 
Gunners,  Master  Electricians,  Engineers  and  Electrician  Sergeants  who  have 
successfully  pursued  the  course  of  instruction  at  the  Coast  Artillery  School. 

Gunpowder. — A  black  or  brown  granular  explosive  mixture  of  low  order, 
made  of  niter,  charcoal  and  sulphur. 

Hang  Fire. — A  delayed  ignition  of  the  powder  charge  caused  either  by 
defective  primer  or  charge.  See  MISSFIRE. 

Harbor  Charts. — Charts  covering  the  water  area  of  each  fortified  harbor 
within  the  field  of  fire  of  the  armament  at  that  point.  They  are  made  on  a 
scale  of  500  yards  to  the  inch  and  the  area  covered  is  marked  off  in  one -inch 
squares  which  are  numbered  consecutively.  The  outlines  of  the  harbor,  depths 
of  water,  channels,  locations  of  batteries  and  stations  are  accurately  indicated. 
A  chart  mounted  on  a  suitable  board,  with  a  range-scale  arm  pivoted  at  the 
point  indicating  the  station  to  which  it  pertains  is  furnished  each  Battle,  Fire, 
Mine  and  Battery  Primary  Observing  Station. 

High  Angle  Fire. — See  FIRE. 

Hoist.— See  AMMUNITION  HOIST. 

Hoist  Room. — The  room  in  the  battery  containing  the  receiving  table  of 
the  ammunition  hoist. 

Homogeneous. — Of  the  same  kind  or  nature ;  consisting  of  similar  parts  or 
of  elements  of  like  nature. 

Hoops. — In  ordnance,  hoops  are  cylindrical  forgings  concentric  with  the 
tube  of  built-up  cannon,  superimposed  upon  the  tube,  jacket"  or  other  hoops. 

The  "A"  Row  are  over  the  jacket,  extending  from  the  breech  to  the  trun- 
nions. 

The  "  B  "  Row  when  used  are  on  "  A  "  Row. 

The  "C"  Row  are  all  those  hoops  in  contact  with  the  tube  in  front  of  the 
jacket. 

The  "D"  Row  are  over  the  front  end  of  the  jacket  and  the  "  C  "  Row  in  front 
of  the  trunnions. 

Horizontal. — On  a  plane  parallel  to  the  horizon. 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  31 

Horizontal  Angle. — An  angle  measured  in  the  horizontal  plane,  or  whose 
sides  lie  wholly  in  such  plane. 

Horizontal  Base  System. — The  system  of  range -finding  in  which  the  posi- 
tion and  range  of  the  target  are  definitely  located  by  the  use  of  the  primary  and 
secondary  arms  of  the  plotting  board,  from  azimuth  readings  taken  simultane- 
ously at  the  primary  and  secondary  observing  stations. 

Horizontal  Plane. — That  plane  which  passes  through  or  contains  the  line 
of  the  horizon.  The  horizontal  plane  referred  to  in  the  artillery  position  finding 
service  is  the  horizontal  plane  containing  the  water  level. 

Horizontal  Position  Finder. — The  Azimuth  instrument. 

Horizontal  Range. — The  longitudinal  distance  from  the  muzzle  of  the  gun 
to  the  point  of  fall  measured  in  the  initial  plane.  It  is  the  range  given  in  all 
fundamental  range  tables. 

Horizontal  Velocity. — The  component  of  the  muzzle  velocity  parallel  to  the 
horizontal  plane  passing  through  the  muzzle  of  the  gun. 

Howitzers. — Those  cannon  whose  relative  length  and  caliber  range  between 
the  gun  and  mortar  classes.  They  are  used  principally  by  the  mobile  army. 

Hydraulic  Jack. — A  portable  machine  for  exerting  great  pressure  for  lifting 
or  moving  a  heavy  body  through  a  small  distance  by  hydraulic  power. 

Hygrometer. — An  instrument  for  measuring  the  degree  of  moisture  in  the 
atmosphere. 

Hypothetical  Targets. — Imaginary  targets  of  assumed  dimensions,  for 
heavy  guns.  This  target  is  outlined  by  two  standard  pyramidal  targets  towed 
60  feet  from  center  to  center  with  a  red  streamer  suspended  from  a  wire  or 
hemp  cord  midway  between  them,  the  hypothetical  target  represented  being  a 
vertical  rectangle  30  by  60  feet.  For  mortars  the  hypothetical  target  is  a 
circle  100  yards  in  diameter  the  center  of  which  is  indicated  by  a  pyramidal 
target. 

Identification  of  Target. — The  act  or  process  of  recognizing  a  target  which 
has  been  designated. 

Igniter  or  Igniter  Charge. — A  small  charge  of  rifle  powder  placed  in  con- 
tact with  the  propelling  charge  to  insure  the  ignition  of  the  latter.  See  PRIMER 
CHARGE. 

Igniting  Primer. — Primers  used  in  cartridge  cases  for  subcaliber  tubes  not 
provided  with  percussion  firing  mechanism.  They  require  for  ignition  an 
auxiliary  friction  or  electric  primer  which  is  inserted  in  the  vent  of  the  spindle 
in  the  same  manner  as  for  service  firing. 

In  Battery. — The  term  used  to  indicate  that  a  gun  is  in  its  proper  position 
for  firing. 

In  Commission. — The  term  used  to  indicate  those  batteries  to  which  per- 
sonnel is  assigned. 

In  Service. — The  term  used  to  indicate  those  batteries  to  which  personnel 
is  assigned  and  at  which  daily  drills  are  held. 

Indication  of  a  Target. — Any  method  employed  to  designate  a  target. 

Inflammation. — The  spread  of  flame  over  the  surface  and  into  the  perfora- 
tions of  powder  grains. 

Illuminating  Light. — A  searchlight  whose  primary  function  is  to  follow  a 
target  that  has  been  assigned  to  a  fire  command. 

Initial  Pressure. — The  first  or  starting  pressure.     The  term  is  frequently 


32  THE  SERVICE  OF  COAST  ARTILLERY 

applied  in  reference  to  initial  tension,  or  the  stress  developed  in  the  body  of  a 
built-up  gun,  by  the  method  of  fabrication.  Initial  tension  is  produced  by 
shrinking  over  a  tube  or  hoop  a  heated  hoop  that  will  have  a  slightly  smaller 
diameter  when  cooled,  each  hoop  compressing  the  one  beneath  it. 

Initial  Velocity. — The  rate  of  travel  at  which  a  projectile  leaves  the  muzzle 
of  a  cannon.  Generally  called  muzzle  velocity. 

Initial  Velocity  of  Rotation. — The  rate  of  motion  at  which  a  projectile  is 
traveling  around  its  longer  axis  at  the  instant  it  leaves  the  muzzle  of  the  gun. 

Initial  Velocity  of  Translation. — The  rate  of  motion  at  which  a  projectile 
is  traveling  in  the  direction  of  its  flight  at  the  instant  it  leaves  the  muzzle  of  the 
gun.  See  MUZZLE  VELOCITY. 

Inside  of  a  Beam. — A  point  is  so  called  when  it  lies  between  the  battle 
commander's  station  and  a  line  passing  through  the  axis  of  a  searchlight  beam. 

Intelligence  Line. — A  telephone  line  connecting  a  primary  and  secondary 
station;  used  for  the  transmission  of  general  information.  The  line  over  which 
data  are  sent  from  the  reader  at  the  secondary  station  to  the  secondary  arm 
setter  at  the  plotting  board  in  the  primary  station  plotting  room  is  called  the 
data  line. 

Interior  Crest. — The  line  of  intersection  of  the  interior  wall  or  slope  with 
the  superior  slope. 

Interior  Slope  or  Wall. — The  inner  slope  or  wall  of  gun  parapets  or  mortar 
pits. 

Intermediate  Armament. — The  armament  of  a  coast  artillery  fort  used  to 
attack  lightly  armored  or  unarmored  vessels;  it  may  be  employed  effectively 
to  supplement  the  primary  armament  in  the  attack  of  armored  vessels,  or  the 
secondary  armament  in  the  defense  of  the  mine  fields.  It  includes  the  6-inch, 
5-inch  and  4.72-inch  guns. 

Jacket. — A  cylindrical  forging,  concentric  with  and  shrunk  on  the  tube; 
it  generally  extends  from  the  breech  of  the  gun  to  a  plane  beyond  the  trunnions. 

Judgment  Firing. — See  OBSERVATION  FIRING. 

Jump,  Angle  of. — The  angle  included  between  the  line  of  departure  and  the, 
axis  of  the  bore  when  the  piece  is  pointed.  Experience  has  shown  that  the 
actual  range  for  a  given  elevation  does  not  correspond  to  the  computed  range. 
For  convenience  it  is  assumed  that  the  entire  discrepancy  is  due  to  an  increase 
or  decrease  of  the  elevation  of  the  gun  at  the  instant  the  projectile  leaves  the 
muzzle,  and  this  small  difference  in  angle  is  called  the  jump.  Therefore  in 
determining  the  sight  or  quadrant  elevation  to  be  used  to  obtain  a  given  range, 
a  correction,  which  differs  for  different  guns,  carriages  and  ranges,  must  be 
applied  to  the  angle  of  departure  given  in  the  range  table.  It  may  be  deter- 
mined by  experiment.  In  practice  it  is  included  in  the  necessary  range  cor- 
rections as  determined  by  trial  shots. 

Junction  Box. — A  device  used  in  splicing  cable,  its  object  being  to  protect 
the  joint  and  cause  the  strain  to  come  upon  the  armor  of  the  cable  rather  than 
on  the  joint  itself. 

The  Single  function  box,  small,  consists  of  two  rectangular  plates  of  cast 
iron  ^-inch  in  thickness,  20  inches  long  and  6  inches  wide,  united  by  four  ^-inch 
bolts  at  the  corners  (the  bolts  having  square  shanks  and  hexagonal  nuts  to 
facilitate  clamping) ;  the  plates  are  hollowed  in  the  middle  to  form  a  chamber 
which  receives  the  turks'  heads  and  joint.  The  ends  of  the  plates  are  curved 


DEFINITIONS,  ABBREVIATIONS  AND   SIGNS  33 

to  admit  the  cable  ends,  and  the  turks'  heads  are  clamped  to  the  lower  plate 
by  straps  and  screw  bolts,  the  cavity  of  the  upper  plate  covering  them  when 
bolted  in  position.  This  type  of  box  is  used  in  splicing  single  conductor  cable. 

The  Single  junction  box,  large,  is  similar  in  construction  and  is  used  in 
splicing  multiple  cables  or  cables  of  more  than  one  core. 

The  Grand  junction  box,  or  junction  box  used  as  a  distribution  box  when  7 
conductor  multiple  cable  is  used,  consists  of  two  circular  plates  of  cast  iron, 
f-inch  in  thickness  and  21  inches  in  diameter,  united  by  four  1-inch  bolts  at 
tne  corners.  The  joints  and  7  conductors  and  multiple  cable  are  clamped  in 
the  box  in  a  similar  manner  to  thai  described  for  the  single  junction  boxes. 

Kentledge. — Old  cast  iron  articles  which  have  become  unserviceable,  such 
as  condemned  guns,  shot  and  shell,  etc. 

Laflin  &  Rand  Firing  Machine,  or  Electric  Firer. — See  EXPLODER. 

Land  Front. — Those  portions  of  the  defenses  which  are  provided  to  repel 
an  attack  from  the  land  area  in  rear  of  or  on  the  flank  of  permanent  seacoast 
works. 

Lands. — In  ordnance,  the  surfaces  or  ribs  of  the  bore  between  two  adjacent 
grooves  of  the  rifling. 

Lanyard. — A  strong  cord  to  one  end  of  which  a  brass  hook  is  attached. 
Used  for  exploding  the  friction  primer  when  the  piece  is  to  be  fired.  See  SAFETY 
LANYARD. 

Large  Caliber  Guns. — The  class  of  guns  included  in  the  primary  armament. 

Lateral. — Of  or  pertaining  to  the  sides. 

Latrine. — A  closet  for  soldiers  in  camps  or  barracks. 

Laying. — The  operation  of  giving  a  gun  the  direction  and  elevation  neces- 
sary to  hit  the  target  without  the  use  of  a  sight. 

Least  Dimension. — A  term  used  in  connection  with  powder  grains.  The 
least  dimension  of  a  grain  of  powder  is  the  dimension  measured  between  the 
perforations  of  a  multi-perforated  grain  over  or  through  which  the  fire  spreads 
in  order  to  consume  the  entire  grain.  See  CRITICAL  DIMENSION. 

Le  Boulenge  Chronograph. — See  CHRONOGRAPH. 

Length  of  the  Bore. — The  distance  from  the  front  face  of  the  breechblock 
when  seated,  to  the  face  of  the  muzzle. 

Limited  Fire. — Fire  delivered  through  a  restricted  circumference  of  an 
azimuth  circle. 

Limits  of  Fire. — The  terminating  azimuths  of  the  field  of  fire  of  a  battery, 

Line. — A  line  is  that  which  has  length,  but  not  breadth  nor  thickness.  A 
curve  or  curved  line  is  a  line  having  no  finite  portion  of  a  straight  line. 

Line  of  Collimation. — The  line  in  which  the  optical  axis  of  the  telescope 
should  be  when  properly  adjusted.  The  line  of  collimation  and  the  line  repre- 
senting the  axis  of  the  telescope,  when  in  proper  adjustment,  coincide. 

Line  of  Defense. — In  coast  artillery,  the  coast  line;  it  consists  of  fortified 
and  unfortified  portions.  The  fortified  portions  are  those  which  include  im- 
portant harbors,  cities,  roadsteads,  estuaries  and  approaches  thereto.  The 
unfortified  portions  are  those  lying  between  or  adjacent  to  the  fortified  portions. 

Lines  of  defense  for  both  the  coast  guard  and  coast  artillery  supports  are 
determined  upon  and  planned  in  detail  in  time  of  peace  for  each  fortification; 
the  works  necessary  for  each  line  are  surveyed  and  mapped  out  in  detail. 

Line  of  Departure. — A  line  representing  the  prolongation  of  the  axis  of  the 


34  .  THE  SERVICE  OF  COAST  ARTILLERY 

gun  at  the  instant  the  projectile  leaves  the  bore ;  it  is  therefore  tangent  to  the 
trajectory  at  the  muzzle.  It  is  sometimes  called  the  line  of  fire. 

Line  of  Direction. — A  line  in  the  vertical  plane  from  the  gun  to  the 
center  of  the  target  at  the  instant  the  shot  strikes. 

Line  of  Impact. — The  line  tangent  to  the  trajectory  at  the  point  of  impact. 

Line  of  Shot. — The  line  from  the  gun  to  the  point  of  impact. 

Line  of  Sight. — A  straight  line  passing  through  the  sights  of  the  piece; 
at  the  instant  of  firing  this  line  passes  through  the  target. 

Litmus. — A  dye  stuff  extracted  from  certain  lichens  as  a  blue  amorphous 
mass  which  consists  of  a  compound  of  the  alkaline  carbonates,  with  certain 
coloring  matters  relating  to  orcin  and  orcein.  When  litmus  is  used  as  a  dye 
it  is  turned  red  by  acids  and  restored  to  its  blue  color  by  alkalies  (common 
salt  is  a  good  one). 

Litmus  Paper. — Paper  saturated  with  blue  or  red  litmus,  used  in  testing 
for  acids  or  alkalies.  It  is  essential  to  the  service  in  that  it  is  used  for  testing 
powder  and  explosives  to  determine  whether  or  not  they  are  deteriorating  in 
storage ;  which  fact  is  indicated  when  the  blue  litmus  paper  is  turned  red  in  the 
presence  of  acid  fumes  which  are  given  off  to  a  greater  or  less  extent  when  a 
powder  or  explosive  is  deteriorating.  The  amount  of  deterioration  is  indicated 
by  the  length  of  the  time  required  for  the  paper  to  change  color. 

Loading  Platform. — That  surface  upon  which  the  cannoneers  stand  while 
loading  the  piece. 

Loading  Position. — At  gun  batteries;  breech  closed,  cannoneers  at  posts 
for  inspection,  projectile  and  powder  charges  on  truck  near  the  delivery  table. 

At  mortar  batteries;  mortars  horizontal,  breech  closed,  cannoneers  except 
No.  6,  at  post  of  inspection,  projectiles  on  trucks  about  ten  feet  in  rear  of 
mortars,  powder  at  entrance  to  pit,  No.  6  is  at  the  entrance  to  the  powder 
magazine. 

Loading  Room. — A  room  suitably  equipped  for  the  loading  of  submarine 
mines. 

Loading  Tray. — A  device  used  to  protect  the  breech  while  loading. 

Location  of  a  Target. — The  determination  of  its  range  and  azimuth  from 
a  given  point.  See  RELOCATION  OF  A  TARGET. 

Longitudinal. — Extending  in  length;  running  lengthwise.  The  longi- 
tudinal extent  of  a  gun  would  be  its  length  from  breech  to  muzzle. 

Long  Roll. — A  drum  alarm  signal,  when,  if  practicable,  each  man  goes 
direct  to  his  post  at  a  run. 

Lug. — A  projecting  piece  to  which  anything  is  attached,  or  against  which 
anything  bears,  or  through  which  a  bolt  passes. 

Lyddite. — A  high  explosive  of  British  manufacture. 

Machine  and  Rapid-Fire  Gun  Mounts. — Guns  of  this  class  used  in  coast 
defense  are  mounted  on  moving  or  traveling  carriages,  and  fixed  mounts,  called 
rapid-fire  mounts,  which  are  disappearing  or  non-disappearing,  recoil  or  non- 
recoil. 

Machine  Guns. — Guns  of  one  or  more  barrels  using  fixed  ammunition  and 
provided  with  mechanism  for  continuous  loading  and  firing.  The  mechanism 
may  be  operated  by  man  power  or  by  the  force  of  recoil.  They  are  designed 
to  deliver  a  strong,  rapid,  continuous  and  accurate  fire  of  small  projectiles. 
See  AUTOMATIC  MACHINE  GUNS  and  SEMI-AUTOMATIC  MACHINE  GUNS. 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  35 

Magazine. — In  a  literal  sense  any  place  where  stores  are  kept;  as  a  military 
expression  a  magazine  signifies  rooms  and  galleries  for  the  storage  of  powder, 
primers,  fuses,  etc.  Magazines  are  classified  as  peace  magazines  and  storage 
magazines. 

Main  Bore. — That  part  of  the  bore  in  front  of  the  forcing  cone. 

Maneuvering  Rings. — Large  cast  iron  rings  fastened  in  the  walls  of  em- 
placements, designed  for  holdfasts  in  mechanical  maneuvers. 

Manning  Party. — The  personnel  assigned  to  the  service  of  any  specific 
element  of  the  defense. 

Manning  Table. — A  list  of  the  names  of  those  who  constitute  a  manning 
party,  with  the  particular  post  to  which  each  is  assigned. 

Mark  One. — A  term  used  to  indicate  the  first  improvement  of  the  original 
model  of  a  particular  type  of  gun,  mortar,  etc. 

Marine  Obstructions. — Sunken  hulks,  subwater  piles,  dams,  booms,  barri- 
cades, rope  entanglements  and  any  other  form  of  barrier  that  may  delay  the 
enemy  in  navigating  a  defended  water  area. 

Masking  Mount. — See  CARRIAGE  or  MOUNT. 

Master  Electrician. — A  non-commissioned  staff  officer  charged  with  the 
general  supervision  of  the  electrical  and  power  installations  of  an  artillery 
district  or  post.  He  assists  the  artillery  engineer  in  his  work  and  is  required  to 
make  inspections  and  tests  of  electrical  plants  and  installations,  and  perform 
such  other  technical  duties  as  may  be  necessary.  Insignia :  Gold  wreath  with 
red  forked  lightning  within  and  a  small  white  star  about  one-half  of  an  inch 
above  the  red  lightning,  all  to  be  of  silk  embroidery  thread. 

Master  Gunner. — A  non-commissioned  staff  officer  employed  in  photo- 
graphic work  and  seacoast  engineering,  in  the  preparation  of  tables,  charts 
and  maps,  and  for  such  other  technical  artillery  duties  as  he  may  be  qualified 
to  perform.  Insignia:  Gold  wreath,  inclosing  a  red  projectile  and  a  small 
white  star  about  one-half  of  an  inch  above  the  projectile,  all  to  be  of  silk  em- 
broidery thread. 

Material  Target. — A  target  used  for  all  subcaliber  practice  with  guns. 
When  used  as  a  fixed  target  it  is  moored  fore  and  aft,  as  nearly  broadside  to 
the  battery  firing  as  possible.  For  battle,  fire  and  mine  command  practice 
two  or  more  targets  are  used  on  the  same  towline,  separated  by  about  100  yards. 
For  record  subcaliber  practice  at  moving  targets  it  is  towed  at  the  end  of  a  300- 
yard  towline.  The  standard  material  target  for  use  as  stated  above  consists 
of  a  buoyant  base  upon  which  is  mounted  a  vertical  rectangular  frame  10x24 
feet,  covered  to  within  2  feet  of  the  bottom  with  white  cotton  cloth  divided 
into  three  panels,  the  middle  panel  being  painted  black.  The  base  consists 
of  two  parallel  flotation  sills  each  of  a  10x10  inch  timber,  surmounted  by  a 
3x10  inch  plank  nailed  thereto;  three  cross-pieces,  a  prow  and  four  diagonal 
braces,  the  whole  being  fastened  with  a  bridle  for  towing. 

All  record  firing  for  rapid  fire  guns  below  4.7-inch  caliber  is  made  with  the 
above  size  of  target.  For  guns  above  4-inch  the  standard  material  target 
30  feet  high  by  60  feet  long  is  used.  See  PYRAMIDAL  TARGET,  HYPO- 
THETICAL TARGET. 

Maul. — A  heavy  wooden  beater  or  hammer,  used  in  driving  stakes,  tent 
pegs,  etc.  Usually  miscalled  mallet  by  inexperienced  soldiers. 

Maximite. — A  high  explosive  shell  filler.     It  is  fusible  and  very  suitable  for 


36  THE  SERVICE  OF  COAST  ARTILLERY 

armor  piercing  shell,  which  are  charged  by  melting  the  maximite  and  pouring 
it  in. 

Maximum. — The  greatest  value  of  a  variable  quantity  or  magnitude,  in 
opposition  to  minimum,  the  least. 

Maximum  Ordinate. — The  vertical  distance  between  the  line  of  sight  and 
the  summit  of  the  trajectory. 

Maximum  Pressure. — The  greatest  pressure  in  the  bore  of  a  firearm.  The 
pressure  indicated  by  the  pressure  gauge. 

Maximum  Range. — The  greatest  range  obtainable  by  using  the  maximum 
elevation  permitted  by  the  carriage. 

Mean  Lateral  Deviation. — The  arithmetical  mean  of  the  lateral  deviations 
of  the  points  of  impact  of  a  series  of  shots,  from  the  center  of  the  target. 

Mean  Longitudinal  Deviation. — The  arithmetical  mean  of  the  longitudinal 
deviations  of  all  the  points  of  impact  of  a  series  of  shots,  from  the  center  of  the 
target.  For  example,  if  six  shots  were  fired  and  struck  as  follows:  No.  1— 
50  yards  over.  No.  2 — 10  yards  short.  No.  3 — 10  yards  over.  No.  4 — 30 
yards  over.  No.  5 — 2  yards  over.  No.  6 — 12  yards  short.  The  mean  longi- 
tudinal deviation  would  be  114^-6  =  19  yards. 

Measure  of  Uniformity. — The  regularity  in  the  velocity  given  by  a  number 
of  consecutive  shots.  It  is  calculated  by  taking  the  mean  observed  velocity, 
and  from  it  deducting  the  difference  in  velocity  of  each  shot,  and  dividing  the 
sum  of  the  differences  by  the  number  of  shots  fired. 

Mechanic. — A  specially  qualified  artilleryman  holding  the  grade  of  that 
name  in  a  coast  artillery  company.  Insignia:  Two  crossed  hammers  of  red 
cloth. 

Mechanics. — The  science  which  treats  of  the  nature  of  forces  and  of  their 
actions  on  bodies,  either  directly  or  by  the  agency  of  machinery. 

Medium-Caliber  Guns. — Guns  of  4-inch,  4-7-inch,  5-inch  and  6-inch 
caliber. 

Melinite. — A  high  explosive  compound  of  foreign  manufacture 

Melting  and  Thawing  Explosives. — The  explosive  shell  filler  maximite  is 
melted  by  placing  it  in  a  copper  watertight  vessel  and  immersing  it  in  a  boiling 
water  bath,  the  temperature  being  kept  practically  at  212  degrees  F.  Dyna- 
mite is  thawed  by  putting  the  cartridges  or  sticks  of  frozen  dynamite  in  a  water- 
tight vessel  and  immersing  it  in  warm  water.  If  sufficient  time  is  available 
a  better  method  would  be  to  leave  the  boxes  open  for  several  hours  in  a  warm 
room  or  by  taking  the  cartridges  out  of  the  boxes  and  laying  them  on  a  shelf 
in  a  room  at  which  the  temperature  is  about  70  degrees  F.,  and  thus  allow  the 
cartridges  to  thaw  out  gradually. 

Mensuration. — The  act  or  process  of  measuring.  That  branch  of  applied 
geometry  which  gives  rules  for  finding  the  length  of  lines,  the  areas  of  surfaces, 
etc.,  from  certain  simple  data  of  lines  and  angles. 

Mercurial  Barometer. — An  instrument  used  in  the  meteorological  station 
to  determine  the  pressure  or  density  of  the  atmosphere. 

Meteorological  Message. — The  message  sent  to  fire  commanders  by  a 
meteorological  observer.  It  includes  the  barometer  and  thermometer  readings, 
the  atmosphere  reference  numbers  and  the  velocity  and  azimuth  of  the  wind. 

Meteorological  Observer. — An  enlisted  man  in  charge  of  the  meteorological 
station. 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  37 

Meteorological  Station. — A  station  containing  instruments  for  obtaining 
and  sending  out  to  the  various  primary  stations  data  relating  to  the  density 
of  the  atmosphere  and  the  velocity  and  direction  of  the  wind. 

Micrometer. — An  instrument,  used  with  a  telescope,  for  measuring  minute 
distances  or  apparent  diameters  of  objects  which  subtend  minute  angles.  The 
measurement  given  directly  is  that  of  the  image  of  the  object  formed  at  the 
focus  of  the  object  glass. 

Micrometer  Caliper  or  Gauge. — A  caliper  or  gauge  with  a  micrometer 
screw  for  measuring  dimensions  with  great  accuracy. 

Military  Crest. — The  military  crest  is  that  part  of  a  hill  or  mountain,  from 
which  all  or  a  greater  part  of  the  downward  slope  within  range  can  be  seen 
and  subjected  to  direct  fire.  It  generally  differs  from  the  actual  or  topo- 
graphical crest,  which  is  at  the  highest  point  or  watershed. 

Mine. — See  SUBMARINE  MINE. 

Mine  Command. — Such  portions  of  submarine  defenses  and  rapid-fire  guns 
for  the  protection  thereof  as  may  be  efficiently  controlled  by  one  man. 

A  mine  command  consists  normally  of  one  or  more  rapid-fire  batteries,  with 
the  necessary  elements  for  a  complete  mine  system,  including  proper  installation, 
control  and  repair  of  the  mine  fields.  There  may  be  more  than  one  mine  com- 
mand in  a  battle  area,  depending  upon  the  size  of  the  harbor  and  the  mine 
defenses  necessary  for  the  protection  thereof. 

Mine  Commander. — A  coast  artillery  officer  assigned  as  such  in  orders  from 
district  headquarters.  He  exercises  both  administrative  and  tactical  command 
of  a  mine  command. 

As  an  administrative  officer  it  is  his  duty  to  have  his  command  supplied 
with  all  material  necessary  for  carrying  out  the  improved  scheme  of  submarine 
defense.  In  this  he  is  assisted  by  a  property  officer,  who  is  responsible  to  the 
mine  commander  for  the  material  and  equipment  of  the  command. 

Tactically  the  mine  commander  is  responsible  to  his  battle  commander  for 
the  condition  of  the  submarine  defense  material  of  his  command  and  the  effi- 
cient service  thereof  at  drill  or  in  action. 

He  is  responsible  for  the  instruction  of  the  officers  and  men  of  his  command 
in  all  matters  pertaining  to  the  care  and  use  of  the  mine  defense  material  and 
rapid-fire  guns  assigned  to  his  command. 

In  battle -command  drill  and  in  action  he  undertakes  to  destroy  such  vessels 
crossing  the  mine  field  as  the  battle  commander  may  direct.  When  ordered 
to  exercise  independent  fire  action  he  fires  the  mines  in  accordance  with  his 
own  judgment.  He  exercises  the  same  command  over  rapid-fire  batteries 
assigned  to  the  mine  command,  as  is  the  case  in  fire  commands. 

He  has  control  over  and  is  responsible  under  the  battle  commander,  for, 
the  use  of  the  mine  field  searchlights. 

Mine  Company. — A  company  assigned  to  the  service  of  submarine  mines. 

Mine  Field. — The  area  of  water  in  which  submarine  mines  are  planted. 

Mine-Field  Lights. — Searchlights  that  may  be  used  for  searching  when 
no  attack  on  the  mine  field  is  anticipated,  and  to  illuminate  the  channel  for  the 
purpose  of  aiding  the  entrance  of  friendly  vessels.  During  an  attack  on  the 
mine  field  their  function  is  to  deceive  the  enemy  by  searching  over  an  area 
outside  the  field.  The  mine  field  should  not  be  illuminated  until  the  enemy's 
boats  approach  one  of  the  fields. 


38  THE  SERVICE  OF  COAST  ARTILLERY 

Mine-Field  Officer. — A  coast  artillery  officer  in  charge  of  laying  and  main- 
taining the  mine  field. 

He  is  responsible  that  the  planting  and  loading  sections  perform  their  duties 
correctly  and  that  proper  material  is  used  in  the  assembling  and  planting  of 
mines ;  that  all  precautions  for  safety  are  taken  in  loading,  planting  and  taking 
up  of  mines. 

Mine  Planter. — A  seagoing  tug  150  feet  in  length  and  about  30  feet  beam. 
It  has  large  deck  space  forward  and  little  rigging.  It  is  equipped  with  booms, 
winches,  davits,  catheads,  triplex  blocks,  etc.,  necessary  in  handling  and  plant- 
ing assembled  mines. 

Mining  Casemate. — A  protected  building  containing  the  controlling  mech- 
anism of  the  mine  defense. 

Minus  Correction. — When  conditions  require  the  use  of  a  range  less  than 
the  actual  range  it  is  termed  minus  correction. 

Minus  Deflection. — A  piece  is  said  to  have  minus  deflection  when  its  axis 
points  to  the  left  of  the  target. 

Misfire. — The  failure  of  a  powder  charge  to  explode.  In  case  of  a  misfire 
in  artillery  practice  the  breech  will  not  under  any  circumstances  be  opened  for 
ten  minutes,  nor  until  the  primer  has  been  removed,  except  when  the  primer 
is  seated  in  the  cartridge  case. 

Miter  Wheel. — See  BEVEL  WHEEL. 

Moat. — See  DITCH. 

Mobile  Torpedo. — Ordinarily  a  cigar-shaped  metal  case  containing  an 
explosive  charge  and  firing  device;  intended  to  run  under  the  surface  of  the 
water  and  attack  the  hull  of  an  enemy's  vessel.  There  are  two  classes,  dirigible 
and  automatic.  The  former  is  controlled  by  electrical  or  other  cables;  the 
latter  carry  their  own  propelling  agent  and  keep  a  given  direction  automatically. 
The  latest  type  of  automobile  torpedo,  known  as  the  Whitehead  torpedo,  is  now 
used  almost  exclusively.  This  torpedo  is  made  of  steel  or  phosphor-bronze, 
about  15  feet  long  and  19  inches  in  diameter,  divided  into  compartments  and 
carrying  a  large  explosive  charge  forward  which  is  fused  and  explodes  on  impact. 
Their  functions  in  coast  defense  are  as  adjuncts  to  fixed  mines,  to  cover  waters 
of  channels  too  deep  or  too  swift  to  mine.  They  are  usually  fired  from  above 
water  from  launching  tubes  located  ashore. 

Monitors. — Armored  vessels  with  very  low  freeboard  and  10-inch  and 
12-inch  gun  turrets,  one  fore  and  one  aft,  of  11-inch  armor.  Average  dis- 
placement 3,000  to  4,000  tons ;  length  250  feet ;  beam  50  to  60  feet.  Armament 
usually  consists  of  10-inch  and  12-inch  guns  and  light  rapid-fire  guns  on  upper 
decks.  The  principal  functions  of  monitors  are  to  supplement  the  regular 
fortifications  of  coast  defense. 

Mortar. — A  cannon  employed  to  throw  projectiles  at  high  angles  of  eleva- 
tion. Their  length  of  bore  is  small  in  comparison  with  the  caliber. 

Mortar  Battery. — The  entire  structure  erected  for  the  emplacement,  pro- 
tection and  service  of  one  or  more  pits  of  mortars. 

Mortar  Company. — A  company  assigned  to  the  service  of  mortars. 

Mortar  Pit.— See  PIT. 

Mount. — See  CARRIAGE  or  MOUNT. 

Mounting  Cannon. — The  mechanical  maneuvers  necessary  to  place  coast 
cannon  in  position. 


DEFINITIONS,  ABBREVIATIONS  AM)  SIGNS  39 

Movable  Armament. — Small  caliber  guns  on  wheeled  mounts,  such  as  the 
Colt  automatic  and  Gatling  machine  gun. 

Movable  Carriage  or  Wheeled  Mount. — A  carriage  or  mount  provided  with 
wheels  for  ready  transportation  of  the  piece  mounted  thereon. 

Mushroom  Head. — The  front  face  of  the  obturator. 

Muzzle. — The  front  end  of  a  cannon,  including  the  mouth  of  the  bore,  the 
face  and  the  swell. 

Muzzle  Velocity. — The  rate  of  travel  at  which  a  projectile  leaves  the  muzzle 
of  a  cannon.  It  is  sometimes  called  initial  velocity. 

Nitro-Cellulose  Powder. — The  name  applied  to  a  form  of  smokeless  powder 
used  in  modern  ordnance,  in  which  cellulose  (unspun  cotton  waste)  is  the  base. 

Nitro-Glycerine  Powder. — The  name  applied  to  a  form  of  smokeless  powder 
used  in  modern  ordnance,  in  which  nitro -glycerine  is  the  base. 

Non-commissioned  Staff  Officers. — The  Coast  Artillery  Corps  non-commis- 
sioned staff  officers  consist  of  sergeants  major,  senior  grade;  master  electri- 
cians, engineers,  electrician  sergeants,  first  class;  electrician  sergeants,  second 
class;  master  gunners,  sergeants  major,  junior  grade,  and  firemen.  They  are 
appointed  after  due  examination,  and  receive  warrants  signed  by  the  Chief  of 
Coast  Artillery. 

Nose. — A  name  sometimes  given  to  the  point  of  projectiles. 

Object  Glass. — The  glass  in  a  telescope  which  is  placed  at  the  end  of  the 
tube  nearest  the  object. 

Oblique  Fire. — Fire  which  is  directed  obliquely  to  the  object  fired  at. 

Observation  Firing. — A  term  applied  to  one  of  the  three  methods  of  ex- 
ploding submarine  mines,  i.e.,  where  the  time  of  firing  is  given  from  the  mine 
commanders'  station. 

Observation  Telescope. — A  telescope  used  in  target  practice  and  in  action 
to  observe  the  striking  point  of  shots. 

Observer. — A  member  of  the  fire-control  section  who  is  in  charge  of  and 
uses  an  observing  instrument.  Insignia:  First  Class.  Red  triangle  with  a 
red  bar  below  within  a  yellow  circle.  Second  Class.  Same  as  first  class, 
omitting  the  bar.  All  to  be  of  cloth. 

Observing  Interval. — The  time  in  seconds  between  two  consecutive  obser- 
vations on  a  target  (between  two  signals  of  the  time  interval  bell)  during  track- 
ing. The  regular  interval  for  guns  is  15  seconds,  and  for  mortars  30  seconds. 

Observing  Room. — The  room  of  a  primary  station  in  which  the  position - 
finding  instrument  and  necessary  accessories  are  located. 

Observing  Station. — A  position  constructed  in  a  favorable  place  for  observ- 
ing the  field  of  fire.  A  protected  position  constructed  in  a  parapet  or  traverse 
for  the  purpose  of  observation,  commonly  called  "  Crow's  Nest." 

Obturating  Primer. — A  primer  of  any  type  so  constructed  as  to  prevent  the 
escape  of  powder  gas  through  the  vent. 

Obturator. — In  gunnery,  any  device  for  preventing  the  escape  of  gas;  the 
term  includes  the  entire  mechanism. 

Obturator  Head. — The  mushroom  head  of  the  breechblock. 

Occult  Light. — The  act  of  screening  or  shutting  off  the  beam  of  a  search- 
light. 

Offensive  Return. — An  offensive  return,  during  an  engagement  of  mobile 
troops,  consists  in  the  assumption  of  the  offensive  by  the  defender  with  the  pur- 


40  THE  SERVICE  OF  COAST  ARTILLERY 

pose  of  recovering  ground  just  captured  by  the  enemy,  and  of  returning  to  the 
original  position. 

Ogive. — That  curve  of  the  head  of  a  projectile  which  terminates  at  the 
point. 

Oil  Room. — A  room  in  the  emplacement  for  the  storage  of  oil. 

Oils. — The  principal  oils  used  in  the  coast  artillery  service  are :  Hydroline, 
for  filling  recoil  cylinders.  Synovial,  for  lubricating  the  breech  recess  and 
breechlock  of  cannon,  and  general  lubrication  of  the  carriage.  Light  Slushing, 
for  slushing  the  bore  of  cannon  and  all  exposed  surfaces  of  the  carriage.  Lubri- 
cant No.  4^,  for  filling  grease  cups.  Linseed  (boiled),  for  use  on  retraction 
ropes,  mixing  paints,  etc.  Kerosene,  for  cleaning  purposes. 

Omniscope. — An  apparatus  used  in  the  Lake  type  of  submarine  boats  for 
observation,  sighting  and  steering. 

One-Pounder. — A  rapid-fire  gun  whose  projectile  weighs  one  pound.  The 
caliber  1.457-inch  pompom,  Vickers-Maxim  gun  is  an  example  of  this  type. 

Open  Sight. — See  SIGHT. 

Opposite  Angles. — When  two  lines  meet  and  cross  each  other  four  angles 
are  formed,  and  the  opposite  angles  are  equal  to  each  other. 

Orders  of  Fire. — 1.  Unrestricted  Fire.  When  the  only  limitation  imposed 
by  the  fire  commander  upon  the  action  of  a  battery  is  the  assignment  of  a  target, 
the  fire  is  said  to  be  unrestricted.  This  is  the  normal  fire  action  of  a  battery. 

2.  Restricted  Fire.  When  the  range  at  which  to  fire,  the  number  of  shots, 
the  firing  interval,  or  any  other  limitation  except  as  to  target,  is  imposed  upon 
the  action  of  a  battery,  the  fire  is  said  to  be  restricted. 

In  unrestricted  fire,  and  also  in  restricted  fire  when  the  rate  is  not  specified, 
the  fire  should  be  as  rapid  as  possible. 

Ordnance. — The  term  applied  to  artillery  armament  and  the  accessories  and 
stores  pertaining  thereto. 

Ordnance  Machinist. — A  civilian  expert  ordnance  machinist,  resident  at 
each  coast  artillery  fort. 

Ordnance  Officer. — See  ARTILLERY  DISTRICT  ORDNANCE  OFFICER,  POST 
ORDNANCE  OFFICER. 

Ordnance  Sergeant. — A  non-commissioned  staff  officer  charged  with  the  care 
and  preservation  of  all  ordnance  property  at  a  coast  artillery  fort.  Chevrons 
and  Insignia:  Three  bars  inclosing  a  shell  and  a  flame.  All  to  be  of  black 
cloth  piped  with  red. 

Orientation. — The  process  of  adjusting  an  instrument,  gun  or  mortar  in 
azimuth. 

Orientation  Table. — A  table  showing  the  azimuths  and  distances  of  various 
points  in  a  harbor. 

Out  of  Commission. — A  term  applied  to  armament  and  fire-control  stations 
that  are  not  in  such  condition  that  they  could  be  made  ready  for  service  in 
24  hours. 

Out  of  Service. — A  term  applied  to  armament  and  fire-control  stations  to 
which  no  manning  party  is  assigned  but  which  could  be  made  ready  for  service 
in  24  hours. 

Outposts. — Detachments  thrown  out  from  a  force  for  the  purpose  of  pro- 
tecting it  from  surprise. 

Outside  of  a  Beam. — A  point  is  said  to  be  outside  of  a  searchlight  beam 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  41 

when  it  lies  on  the  outer  side  of  a  line  passing  through  the  axis  of  the  beam  as 
seen  from  the  battle  commander's  station. 

Paints  on  Projectiles. — Projectiles  are  painted  so  as  to  show  the  material 
used  in  their  manufacture,  their  armor-piercing  qualities,  their  center  of  gravity 
and  their  character. 

Pantograph. — A  device  used  on  the  plotting  board  of  a  fire-command  sta- 
tion, to  relocate  for  data  for  use  at  any  battery  in  that  command. 

Parade  Slope  or  Wall. — The  rear  slope  or  wall  of  an  emplacement. 

Parados. — Earthworks  in  rear  of  a  battery  for  protection  against  fire  from 
the  rear.  It  may  have  interior,  superior,  exterior  and  traverse  slopes. 

Parallax. — An  apparent  displacement  of  an  object  observed  through  a 
telescope,  due  to  the  real  displacement  of  the  observer,  so  that  the  direction 
of  the  object  with  reference  to  the  observer  is  changed. 

In  optics,  parallax  is  an  apparent  displacement  of  the  image  upon  the  cross- 
wires  in  a  telescope  when  the  eye  is  moved  across  the  eye-piece.  It  is  due  to  the 
non-coincidence  of  the  cross-wires  with  the  focal  plane  of  the  objective.  Both 
the  image,  as  formed  by  the  objective,  and  the  cross  wires,  should  lie  in  the 
focus  of  the  eye-piece,  i.e.,  in  the  same  plane. 

The  image  may  be  moved  back  and  forth  by  moving  the  objective  in  or  out, 
but  the  plane  of  the  cross  wires  is  fixed.  When  the  two  are  brought  into  the 
same  plane  the  image  is  brought  upon  the  cross- wires.  To  accomplish  this  the  eye- 
piece should  first  be  focused  on  the  cross-wires  so  that  they  appear  most  distinct, 
the  irregularities  of  the  wires  being  very  apparent.  There  should  be  no  image 
visible  during  this  operation,  that  is,  the  objective  should  either  be  thrown  out 
of  focus  by  turning  the  focusing  knob  either  all  the  way  out  or  in;  or  the  tele- 
scope should  be  pointed  to  the  sky.  The  eye-piece  should  then  be  moved  until 
the  inner  and  outer  limits  of  distinct  vision  of  the  wires  are  found,  and  then  set 
at  the  mean  position.  The  telescope  should  then  be  pointed  toward  the  object 
and  moved  until  the  image  also  comes  into  focus  accurately.  If  parallax  is 
now  found  it  should  be  removed  by  refocusing. 

The  adjustment  of  the  eye-piece  will  be  correct  for  the  same  observer  re- 
gardless of  the  range  and  object  sighted  upon,  but  it  may  be  necessary  to  refocus 
the  objective  when  the  range  differs  materially. 

Parallel. — Parallel  planes  and  lines  are  the  same  distance  apart  at  all  points; 
if  prolonged  they  will  never  meet. 

Parapet. — That  part  of  a  battery,  composed  of  earth,  timber,  stone,  metal, 
etc.,  which  give  protection  to  the  armament  and  personnel  from  front  fire. 

Patrol  Boats. — Boats  of  the  torpedo-boat  destroyer  type.  During  fog  or 
thick  weather  they  are  necessary  to  guard  the  mine  fields  and  such  independent 
mine  groups  as  are  not  covered  by  the  shore  defenses;  also,  at  night,  they 
patrol  the  approaches  within  the  battle  area  with  the  object  of  preventing  the 
small  craft  of  the  enemy  from  stealing  into  the  inner  waters,  under  cover  of 
darkness  of  the  land  shadows.  In  case  searchlights  are  occulted  or  fail,  the 
boat  patrol  is  the  only  means  available  to  discover  any  movement  of  the  enemy 
and  give  the  alarm. 

Pawl. — A  pivoted  tongue,  sliding  bolt  or  catch,  adapted  to  fall  into  notches 
or  indental  spaces  in  such  a  manner  as  to  permit  motion  in  one  direction  and 
prevent  it  in  the  reverse,  as  in  a  windlass. 

Penetration  of  Projectiles. — The  ability  of  a  projectile  to  overcome  the 


42  THE  SERVICE  OF  COAST  ARTILLERY 

resisting  qualities  of  an  armor  plate  by  completely  or  partially  perforating  it. 
The  ability  to  perform  this  function  depends  on  the  relative  merits  of  the 
particular  projectile,  the  plate  against  which  it  is  fired,  the  striking  velocity 
and  the  angle  of  impact. 

Percussion  Cap. — A  cap  in  which  the  method  of  explosion  is  due  to  a  blow; 
used  in  fixed  ammunition. 

Percussion  Fuse. — A  fuse  which  is  armed  or  prepared  for  action  by  the 
shock  of  discharge  and  acts  upon  impact. 

Percussion  Primer. — The  type  of  primer  used  in  fixed  ammunition  which 
is  exploded  by  a  blow  of  the  firing  pin. 

Periscope. — An  apparatus  used  on  the  Holland  type  of  submarine  boat,  for 
observation,  sighting  and  steering. 

Perpendicular. — Exactly  upright  or  vertical ;  at  right  angles  with  the  plane 
of  the  horizon.  When  two  lines  so  intersect  each  other  as  to  form  four  equal 
angles  they  are  said  to  be  perpendicular  to  each  other. 

Personnel. — The  personal  composition  of  any  organized  group  of  officers 
or  men  which  has  for  its  purpose  the  accomplishment  of  some  service. 

Picket  Boats. — Any  speedy  boat  or  boats  stationed  outside  the  battle  area 
to  watch  for  the  enemy  and  give  warning  of  his  approach. 

Picric  Acid. — A  detonating  and  disruptive  explosive  of  high  order  used  as 
a  base  for  explosives  or  shell  fillers. 

Piece. — The  name  applied  to  any  type  of  cannon,  whether  gun  or  mortar. 
It  is  also  used  as  a  matter  of  convenience  to  designate  both  cannon  and  carriage 
when  the  cannon  is  mounted. 

Pit. — That  part  of  a  mortar  emplacement  designed  for  mounting  one  or 
more  mortars,  usually  four. 

Pit  Commander. — A  non-commissioned  officer  (gun  commander)  in  charge 
of  a  mortar  pit. 

Plane. — A  surface  without  curvature  which  has  length  and  breadth  but  no 
thickness;  a  surface  real  or  imaginary,  in  which,  if  any  two  points  are  taken, 
the  straight  line  which  joins  them  lies  wholly  in  the  surface. 

Plane  of  Departure — The  vertical  plane  containing  the  line  of  departure. 

Plane  of  Direction.— The  vertical  plane  containing  the  line  of  direc- 
tion. 

Plane  of  Sight.— The  vertical  plane  containing  the  line  of  sight. 

Planter. — See  MINE  PLANTER. 

Planting  Section. — A  section  of  the  enlisted  personnel  of  a  mine  company, 
consisting  of  men  required  afloat.  It  is  divided  into  a  planter  detachment  and 
the  small  boat  detachments. 

Plotter. — A  specially  qualified  enlisted  man  in  charge  of  the  plotting  board 
at  a  fire-control  station.  Insignia:  Red  triangle  with  a  red  bar  below  within 
a  yellow  circle,  all  to  be  of  cloth. 

Plotting  Board. — A  device  used  in  the  position-finding  service  to  quickly 
plot  to  scale  the  data  sent  from  the  position-finding  instruments,  and  in  con- 
nection with  range  and  deflection  boards,  to  determine  the  corrected  data  for 
firing.  It  consists  essentially  of  a  semi-circular  drawing  board  with  a  radius 
of  45  inches,  made  of  well-seasoned  lumber.  It  has  mounted  upon  it  the  neces- 
sary scale  arms  and  gun  center  to  determine  the  rate  of  travel  of  the 
target  both  in  range  and  azimuth  for  use  on  the  range  and  deflection  boards. 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  43 

By  means  of  the  gun  arm  the  range  and  azimuth  to  the  target  from  the  directing 
point  of  the  battery  is  found. 

Plotting  Room. — The  room  in  which  the  plotting  detachment  works.  It  is 
usually  located  below  and  communicates  with,  the  instrument  room  of  the 
battery  commander's  station,  or  with  the  observing  room  of  the  primary 
station. 

Plunging  Fire. — Fire  in  which  the  line  of  departure  passes  below  the  hori- 
zontal plane. 

Plus  Correction. — When  conditions  require  the  use  of  a  range  greater  than 
the  actual  range  the  correction  is  called  plus  correction. 

Plus  Deflection. — A  piece  is  said  to  have  plus  deflection  when  its  axis  points 
to  the  right  of  the  target. 

Point. — That  which  has  neither  length,  breadth,  nor  thickness — only  posi- 
tion, In  communicating  numerals  a  word  used  as  a  mark  of  division,  i.e.,  a 
period.  For  example,  106.20  would  be  expressed:  "One-zero-six-point-two- 
zero." 

Point  Fuse. — A  firing  device  inserted  in  the  point  of  a  shell  not  intended  to 
penetrate;  as  shrapnel. 

Point  of  Fall. — The  point  of  intersection  of  the  trajectory  where  it  crosses 
the  horizontal  plane  passing  through  the  muzzle  of  the  gun.  See  THEORETICAL 
RANGE 

Point  of  Impact. — The  point  where  the  projectile  first  strikes  on  meeting 
an  opposing  body, 

Pointing. — The  operation  of  giving  a  piece  the  direction  and  elevation  neces- 
sary to  hit  the  target.  When  the  sight  is  used  it  is  called  "aiming";  when 
the  sight  is  not  used,  it  is  called  "laying." 

Position  Angle. — See  ANGULAR  ELEVATION. 

Position  Finder. — An  instrument  for  locating  a  target.  See  AZIMUTH 
INSTRUMENT,  DEPRESSION  POSITION  FINDER,  HORIZONTAL  POSITION  FINDER, 
and  SELF-CONTAINED  POSITION  FINDER. 

Position-Finding     System. — The     system    of    position    finding    includes: 

1.  The  horizontal  base  system,  which  employs  azimuth  reading  instruments 
in  stations  at  the  ends  of  a  base  line,  and  a  plotting  board. 

2.  The  depression -position  finding  system,  which  employs  a  depression -posi- 
tion finder  at  a  considerable  elevation  above  the  sea  level,  and  a  plotting  board. 

3.  The  emergency  system,  which  ordinarily  employs  a  self-contained  instru- 
ment located  at  the  battery,  with  or  without  a  plotting  board. 

Post  Adjutant. — A  coast  artillery  officer  responsible,  under  the  post  com- 
mander, for  the  various  reports,  returns,  rosters,  details,  records,  orders  and 
communications  pertaining  to  the  administration  of  a  post.  It  is  his  duty  to 
sustain  the  reputation,  discipline  and  harmony  of  the  command  under  all  circum- 
stances. He  is  assisted  by  a  sergeant  major  and  as  many  clerks  as  may  be 
required.  His  tactical  duties  are  those  prescribed  for  regimental  or  battalion 
adjutants  of  infantry  and,  unless  otherwise  assigned,  communicating  officer  of  a 
fire  command. 

Post  Artillery  Engineer. — A  coast  artillery  officer  holding  all  engineer  and 
signal  property  at  a  post  on  memorandum  receipt  to  the  district  artillery 
engineer,  and,  except  when  it  is  so  held  by  the  commanding  officer  of  a  com- 
pany or  detachment  assigned  to  the  mine  defense,  he  holds  mine  property  in 


44  THE  SERVICE  OF  COAST  ARTILLERY 

the  same  manner.  He  is  responsible  to  the  post  commander  for  the  care, 
preservation  and  efficiency  of  all  engineer  and  signal  property  under  his  control. 
He  is  charged  with  the  supervision,  test  and  maintenance  of  the  electrical  and 
lighting  plants,  also  searchlights  and  lines  of  electrical  communication.  He  is 
assisted  by  master  electricians,  engineers,  electrician  sergeants,  firemen  and 
such  additional  enlisted  men  as  may  be  necessary.  His  tactical  duties  are 
those  of  searchlight  officer  unless  otherwise  assigned. 

Post  Commander. — The  senior  coast  artillery  officer  assigned  to  dutv  at  an 
artillery  post.  He  has  control,  within  the  limits  of  the  post  and  subject  to 
higher  authority,  of  all  matters  relating  to  coast  artillery,  its  personnel  and 
material.  He  appoints  the  post  staff  officers  on  duty  at  the  post,  corresponding 
to  those  of  an  artillery  district,  unless  the  headquarters  of  an  artillery  district 
is  stationed  at  the  post,  in  which  event  the  artillery  district  staff  officers  serve 
as  the  corresponding  post  staff  officers. 

Post  Commander's  Flag. — See  FLAG  OF  POST  COMMANDER. 

Post  Commissary  Sergeant. — A  post  non-commissioned  staff  officer  in  im- 
mediate charge  of  all  commissary  stores  and  property  at  a  post.  Chevrons  and 
insignia:  Three  bars  and  a  crescent  (points  to  the  front),  all  to  be  of  cadet 
gray  cloth. 

Post  Flag.— The  national  flag,  20-foot  fly  and  10-foot  hoist.  Hoisted  daily 
in  pleasant  weather. 

Post  Non-commissioned  Staff. — Ordnance  sergeants,  post  commissary  ser- 
geants, and  post  quartermaster  sergeants. 

Post  Ordnance  Officer. — A  coast  artillery  officer  charged  with  the  care  of 
all  ordnance  property  not  charged  to  battery  commanders.  He  holds  all  ord- 
nance property  and  stores  pertaining  to  the  modern  seacoast  armament  at  the 
post  on  memorandum  receipt  from  the  artillery  district  ordnance  officer.  He 
is  responsible  that  batteries  out  of  service  are  kept  in  such  condition  that  they 
can  be  prepared  for  service  upon  not  more  than  24  hours'  notice.  He  is  assisted 
by  the  post  ordnance  sergeants  and  necessary  assistants.  His  tactical  duties 
are  those  of  a  company  officer  unless  otherwise  assigned. 

Post  Quartermaster. — An  officer  charged  with  the  care  and  supervision  of 
all  quartermaster  property  at  a  post,  as  well  as  the  receipt  and  issue  of  all 
quartermaster  stores,  etc.  His  tactical  duties,  if  a  coast  artillery  officer,  are 
those  of  company  officer  unless  otherwise  assigned. 

Post  Quartermaster  Sergeant. — A  post  non-commissioned  staff  officer  in  im- 
mediate charge  of  all  quartermaster  property  at  a  post.  Chevrons  and  Insignia: 
Three  bars  of  buff  cloth  and  insignia  of  Quartermaster  Department. 

Post  Telephone  Switchboard. — A  central  telephone  station. 

Powder. — See  GUNPOWDER. 

Powder  Blast. — The  force  of  the  powder  gas  for  a  short  distance  in  front 
of  the  muzzle,  which  acts  destructively  on  objects  close  at  hand  lying  within 
its  path. 

Powder  Cases. — Cases  in  which  powder  is  contained  in  shipment  from 
arsenals  or  storage  until  used.  Three  types  are  in  common  use;  the  zinc 
storage  case  with  balata  washers;  the  wooden  storage  case;  and  the  metallic 
cartridge  case  hermetically  sealed.  The  latter  is  rapidly  replacing  all  the 
others  in  the  service. 

Powder  Chamber. — The  chamber  in  the  bore  for  the  reception  of  the  powder 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  45 

charge;  it  is  usually  cylindrical,  but  frequently  conical  and  sometimes  ellip- 
tical. It  is  between  the  breech  recess  and  the  centering  slope,  which  unites 
it  with  the  forcing  cone. 

Powder  Chart. — A  graphic  chart  used  to  determine  the  velocity  to  be 
expected  from  a  given  charge  of  powder  considered  as  a  function  of  the  tem- 
perature of  the  powder. 

Powder  Chute. — In  gun  emplacements  an  inclined  well  or  shaft  for  returning 
cartridges  or  dummies  to  magazine. 

Powder  Hoist. — A  device  for  raising  powder  from  the  magazine  to  the 
loading  platform. 

Powder  Hoist  Well. — The  shaft  through  which  the  powder  hoist  operates. 

Powder  Magazine. — See  MAGAZINE. 

Powder  Room. — See  CARTRIDGE  ROOM. 

Power  and  Light  Equipment. — Equipment  including  engines,  dynamos, 
storage  batteries,  motors,  electric  and  other  kinds  of  lights,  and  all  material 
and  supplies  pertaining  thereto. 

Power  Room. — A  room  in  the  battery  provided  for  the  necessary  motor 
generators,  induction  motors  and  switch-boards. 

Power  Section. — A  detachment  of  the  enlisted  personnel  of  a  mine  com- 
pany consisting  of  the  operators  and  assistants  required  at  the  power  plants, 
searchlights  and  mining  casemate  of  a  mine  command. 

Power  Station  or  Plant. — The  principal  source  of  supply  of  energy, 
usually  electrical,  for  the  power  system  of  the  fortifications  and  stations. 
The  plant  consists  of  a  sufficient  number  of  direct  connected  units  to  supply 
all  the  power  needed  for  the  entire  installation  under  conditions  of  full  load. 

Predicted  Firing. — Firing  at  which  guns  and  mortars  are  given  direction 
and  elevation  corresponding  to  a  predicted  point. 

Predicted  Point. — A  point  on  the  course  of  a  moving  target,  as  ndicated 
on  the  plotting  board  at  which  it  is  predicted  the  target  will  arrive  at  the  ex- 
piration of  an  assumed  interval  of  time.  This  interval  of  time  is  called  the 
predicting  interval. 

Predicted  Time. — The  time  at  which  the  target  should  reach  a  predicted 
point. 

Predicting  Interval. — See  PREDICTED  POINT. 

Predicter. — An  accessory  of  the  mortar  plotting  board  used  to  locate  the 
position  of  the  predicted  and  set-forward  points. 

Preponderance. — The  excess  (moment)  of  weight  of  that  part  of  the  piece 
in  rear  of  the  trunnions  over  that  of  the  front,  or  the  converse.  It  is  measured 
by  the  force  expressed  in  pounds  necessary  to  balance  the  cannon  when  resting 
freely  on  the  trunnions. 

Pressure  Cylinder. — A  soft  copper  cylinder  used  in  crusher  gauges  which 
is  compressed  by  the  explosion  of  the  charge. 

Pressure  Gauge. — See  CRUSHER  GAUGE. 

Primary  Armament. — The  armament  of  a  coast  artillery  fort  used  to  attack 
the  side,  turret  and  deck  armor  of  war  vessels,  and  carry  large  explosive  charges 
into  their  interiors.  It  includes  the  8-inch,  10-inch,  12-inch,  14-inch  and 
16-inch  guns,  and  12-inch  mortars. 

Primary  Station. — The  principal  station  of  a  base  line.  See  BASE-END 
STATION. 


46  THE  SERVICE  OF  COAST  ARTILLERY 

Primer. — A  wafer,  cap,  tube  or.  other  device  for  communicating  fire  to  the 
powder  charge.  There  are  five  classes  of  primers  used  in  the  U. .  S.  Coast 
Artillery  service,  namely:  Friction,  percussion,  electric,  combination  and 
igniting. 

Priming  Charges. — A  charge  consisting  of  black  powder,  quilted  in  each 
end  of  the  bag  containing  the  sections  of  smokeless  powder  for  the  purpose  of 
igniting  it. 

Prismatic  Powder. — A  molded  gunpowder  hexagonal  in  shape,  with  a 
single  round  perforation  through  the  center  of  the  grain.  It  is  either  brown  or 
black  in  color,  depending  upon  the  color  of  the  charcoal  used.  The  black 
prismatic  powder  is  made  of  the  ordinary  black  granulated  powder,  the  "  can- 
non powder"  grain  being  taken  as  a  base. 

Probability  Factors. — A  table  of  factors  which,  multiplied  by  the  width  of  a 
zone  containing  fifty  per  cent,  of  the  hits,  will  give  the  width  of  zones  contain- 
ing any  other  percentage  of  hits. 

Probability  of  Error. — As  referred  to  gunnery,  is  that  particular  error  in 
any  direction  in  which  it  is  an  even  chance  will  not  be  exceeded  by  any  shot. 
It  is  based  upon  the  rule  that  when  the  value  of  any  quantity  or  element  has 
been  determined  by  means  of  a  number  of  independent  observations,  each  one 
liable  to  a  small  amount  of  accidental  error,  the  result  of  determination  will  also 
be  liable  to  some  uncertainty.  The  probable  error,  therefore,  is  the  quantity, 
which  is  such  that  there  is  some  probability  of  difference  between  the  determi- 
nation and  the  true  absolute  value  of  the  thing  to  be  determined,  exceeding  or 
falling  short  of  it.  The  probable  error  of  a  gun,  in  any  direction,  is  a  distance 
measured  in  that  direction  from  the  center  of  impact,  of  such  length  that  it  is 
an  even  chance  that  it  will  not  be  exceeded  by  a  single  shot,  and  for  which  it 
can  be  predicted  that  in  the  long  run  50  per  cent,  of  all  shots  fired  will  have 
a  less  error. 

Probable  Zone. — The  space  bounded  by  two  parallel  straight  lines  of  such 
length  that  by  the  theory  of  probabilities  50  per  cent,  of  the  points  of  impact 
will  probably  be  found. 

Profile  Board. — A  thin  plate  or  board  having  its  edge  so  cut  as  to  represent 
the  outline  of  an  object ;  it  is  used  to  prove  the  models  of  the  breech  and  other 
exterior  parts  of  a  gun. 

Progressive  Powder. — An  explosive  or  propelling  agent  of  low  order;  for 
example,  the  charcoal  and  nitro-cellulose  powders.  The  explosion  of  powders 
of  this  kind  is  marked  by  more  or  less  progression.  The  mass  is  ignited  at  one 
point  and  the  combustion  proceeds  progressively  over  the  exterior  exposed 
surfaces  and  then  at  right  angles  to  these  surfaces. 

Projectile. — A  term  applied  to  a  missile  usually  thrown  from  a  firearm  by 
some  explosive,  to  strike  and  destroy  some  distant  object.  The  principal  parts 
of  a  modern  projectile  include  the  point  or  nose,  the  ogive,  the  bourrelet,  the 
base,  the  rotating  band  and  the  fuse  hole. 

Projector. — The  technical  name  of  a  searchlight. 

Proof  of  Gunpowder. — A  certain  test  made  on  separate  lots  of  gunpowder 
before  it  is  accepted  by  the  War  Department. 

Proof  Plug. — See  CRUSHER  GAUGE. 

Property  Officer. — The  senior  company  officer  of  a  mine  command.  He  is 
responsible  to  the  mine  commander  that  requisitions  are  made  for  the  necessary 


DEFINITIONS,    ABBREVIATIONS  AND  SIGNS  47 

apparatus  and  material  for  the  mine  defense.  He  has  direct  charge  of  all 
property  appertaining  to  the  care,  loading  and  planting  of  submarine  mines. 

Protractor. — A  mechanical  instrument  used  for  laying  out  and  measuring 
angles  on  paper. 

Pyramidal  Target.— A  material  target  in  the  form  of  a  pyramid,  covered 
with  canvas  painted  vermilion,  divided  into  rectangles  2  feet  wide,  which  are 
painted  alternately  vermilion  and  white.  This  pyramid  is  mounted  on  a 
float  made  of  two  parallel  sills  of  timber,  joined  by  transoms,  two  diagonal 
braces  and  a  prow  to  which  a  suitable  bridle  is  attached  for  towing.  This 
target  is  used  as  a  fixed  target  for  all  trial  shots,  and  in  case  the  material  target 
for  heavy  guns  has  not  been  furnished,  two  of  these  targets  are  towed  60  feet 
from  center  to  center,  with  a  red  streamer  suspended  from  a  wire  or  hemp  line 
at  the  middle  point  between  them,  to  represent  the  material  target.  For 
service  practice  with  mortars  this  target  is  used  to  represent  the  center  of  a 
circular  hypothetical  target  100  yards  in  diameter.  For  subcaliber  practice 
with  mortars  this  target  without  canvas  covering  but  with  a  flagstaff  and  flag 
is  used. 

Quadrant. — The  quarter  of  a  circle  or  the  quarter  of  the  circumference  of  a 
circle ;  an  arc  of  90  degrees.  See  GUNNER'S  QUADRANT. 

Quadrant  Angle  of  Departure. — The  angle  between  the  line  of  departure 
and  the  horizontal  plane  through  the  muzzle.  It  is  obtained  from  the  angle 
of  departure  by  correcting  for  the  angular  elevation  or  depression  of  the  target, 
including  curvature  of  the  earth. 

Quadrant  Elevation. — The  angle  between  the  horizontal  and  the  axis  of 
the  bore  when  the  piece  is  pointed.  It  is  obtained  from  the  angle  of  departure 
by  correcting  for  the  angular  elevation  or  depression  of  the  target  including 
curvature  of  the  earth  and  for  jump. 

Quartermaster. — See  ARTILLERY  DISTRICT  QUARTERMASTER  and  POST 
QUARTERMASTER. 

Quartermaster  Sergeant. — See  POST  QUARTERMASTER  SERGEANT. 

Quick-Firing  Guns. — A  British  term  for  rapid-fire  guns. 

Quickness  of  Burning.— The  rapidity  with  which  a  grain  of  powder  is 
consumed.  When  it  is  said  that  the  powder  is  too  quick  or  too  slow  for  a  gun, 
the  quickness  of  burning  through  the  "critical  dimension"  of  the  grain  is  re- 
ferred to. 

Rack. — A  bar  or  arc,  having  teeth  that  engage  with  those  of  a  gear  wheel 
or  worm. 

Radial  Vent. — A  vent  extending  at  right  angles  to  the  axis  of  the  bore. 

Radius. — Any  line  extending  from  the  center  to  the  circumference  of  a 
circle :  it  is  one-half  the  diameter. 

Rammer. — A  rod  provided  with  a  graduated  brass  ring ;  used  for  properly 
seating  a  projectile  in  the  bore  of  seacoast  cannon. 

Ramp. — An  inclined  plane  or  foot-path,  serving  as  a  means  of  communica- 
tion from  one  level  to  another. 

Rampart. — A  broad  embankment  of  earth  around  a  place  upon  which  a 
parapet  is  raised.  A  structure  forming  the  substratum  of  every  permanent 
fortification. 

Range.— The  range  in  gunnery  is  the  horizontal  distance  from  the  muzzle 
of  the  gun  to  the  target.  The  word  is  applied  in  a  general  sense  to  other  hori- 


48  THE  SERVICE  OF  COAST  ARTILLERY 

zontal  distances,  as,  for  instance,  to  the  distance  between  the  position  finders 
and  the  target,  or  between  a  position  finder  and  a  splash,  etc. 

The  range  of  a  shot  is  the  horizontal  distance  from  the  center  of  the  gun 
to  the  point  where  the  projectile  first  strikes. 

Range-Azimuth  Table. — A  table  of  ranges  and  the  corresponding  azimuths 
from  a  gun  to  points  in  the  center  of  the  main  ship  channel  or  channels.  It  is 
kept  at  the  gun  and  used  for  firing  without  the  use  of  the  range-finding 
apparatus. 

Range  Board. — A  device  for  obtaining  the  range  corrections  which  must  be 
made  for  wind,  atmosphere,  tide,  velocity,  and  travel  of  target  during  the 
observing  interval  and  time  of  flight. 

Range  Deviation. — The  difference  between  the  range  to  the  target  and  the 
range  to  the  point  of  impact. 

Range  Difference. — The  difference  in  range  of  a  point  from  any  other  two 
points,  as,  the  difference  between  the  range  to  the  target  from  the  directing 
gun,  and  the  range  to  the  target  from  any  other  gun  of  the  same  battery. 

Range  Finder. — An  instrument  for  determining  the  range  to  a  target  or 
object,  from  some  fixed  point. 

Range  Keeper. — A  specially  qualified  member  of  the  fire-control  section, 
who  operates  the  time  range  board  and  calls  out  the  range  to  the  range  setter 
as  often  as  may  be  necessary  to  insure  the  piece  being  kept  at  proper  elevation. 
In  restricted  fire  at  a  specified  interval  he  keeps  the  time  and  indicates  to  the 
chief  of  detachment  the  proper  time  to  trip  the  gun. 

Range  of  Ballistic  Tables. — See  THEORETICAL  RANGE. 

Range  Officer. — A  coast  artillery  officer  in  immediate  charge  of  all  or  a 
part  of  the  fire-control  section. 

He  is  stationed  at  the  battery  plotting-room.  He  is  responsible  to  the 
battery  commander  for  the  condition  of  the  material  pertaining  to  the  fire- 
control  service,  for  the  instruction  of  the  fire-control  personnel  and  for  the 
efficiency  of  that  service  in  general.  Upon  opening  the  station  he  should  make 
careful  inspection  of  the  equipment,  verify  the  adjustment  of  the  position- 
finding  instruments,  plotting-board,  etc.  After  satisfying  himself  that  every- 
thing is  in  order  and  receiving  the  reports  of  the  chiefs  of  details,  he  reports  to 
the  battery  commander:  "Sir,  fire-control  stations  in  order,"  (or  reports  defects 
he  cannot  readily  correct). 

In  battle  and  fire-command  drill  or  action,  he  receives  directly  from  the 
fire  commander  and  executes  orders,  as  to  the  assignment  of  targets.  When 
direct  communication  between  the  fire  commander  and  the  battery  commander 
is  impracticable  he  receives  directly  and  executes  other  orders  pertaining  to  the 
fire  action  of  the  battery.  He  is  responsible  to  the  battery  commander  for  the 
prompt  and  accurate  transmission  to  the  battery  commander  of  orders  received 
by  him  from  the  fire  commander. 

At  the  close  of  the  drill  or  action  he  directs  stations  to  be  closed,  inspects 
them  and  reports  to  the  battery  commander,  handing  him  all  records  pertaining 
to  the  work  at  his  station. 

Range  Rake. — An  instrument  made  in  the  form  of  an  ordinary  rake. 
The  main  arm  is  shaped  like  a  gun  stock  with  the  cross  arm  extended  at  front 
end.  At  a  convenient  distance  on  the  main  arm  is  placed  a  guide  peg  repre- 
senting the  rear  sight,  while  on  the  cross  arm  pegs  are  placed  at  intervals  of  one- 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  49 

half  of  an  inch  to  represent  points,  each  point  having  a  value  in  mils  equal 
to  1/1000  the  length  of  the  towline  connecting  the  target  with  the  tug  upon 
which  the  observations  with  the  range  rake  are  taken.  To  use  the  range  rake 
the  observer  takes  position  at  a  point  in  the  center  of  the  stern  of  the  tug  and 
aims  the  rake  so  that  the  line  of  sight  from  the  guide  peg  will  pass  over  the 
center  peg  on  the  cross  arm  and  thence  to  the  target.  At  the  instant  the  splash 
of  the  shot  occurs,  the  observer,  keeping  the  rake  pointed  as  above  described, 
sights  over  the  guide  peg  and  in  the  direction  of  the  splash,  observing  which  peg 
on  the  cross  arm  is  in  line  with  the  splash.  For  example,  if  a  shot  struck  five 
divisions  of  the  rake  beyond  the  target  (or  five  pegs),  assuming  the  value  of 
each  peg  at  10  mils,  the  reading  in  mils  would  be  50;  if  the  towline  wet  mea- 
sured 295  yards,  the  shot  would  have  struck  14.75  yards  over.  This  is  obtained 
as  follows:  50  X  295 -=-1000  =  14.75  yards. 

Range  Scale. — The  graduations  in  yards  either  on  the  range  scale  arc  of 
rapid  fire  guns,  or  the  quadrant  arc  of  large-caliber  guns. 

Range  Setter. — A  specially  qualified  member  of  the  gun  section  who  lays 
the  gun  for  range. 

Range  of  a  Shot. — See  RANGE. 

Range  Table. — A  properly  constructed  range  table  for  a  particular  piece, 
containing  the  range,  time  of  flight,  drift,  etc.,  for  each  elevation. 

Rapid-Fire  Gun. — A  single-barrel  breech-loading  gun  provided  with  breech 
mechanism,  mounting,  and  facilities  for  loading,  aiming  and  firing  with  great 
rapidity.  The  breech  mechanism  is  operated  by  a  single  motion  of  the  handle 
or  lever.  The  smaller  calibers  use  fixed  ammunition. 

Rapid-Fire  Gun  Carriage. — See  CARRIAGE  or  MOUNT. 

Rate  of  Fire. — The  average  rate  of  fire  of  heavy  caliber  guns  with  service 
charge  should  be  about  one  shot  in  forty  or  fifty  seconds. 

Ratings. — A  particular  class  or  grade  to  which  enlisted  men  belong.  In  the 
coast  artillery  they  may  be  rated  as  sergeants  major,  master  electricians, 
engineers,  electrician  sergeants,  master  gunners,  firemen,  casemate  electricians, 
observers,  plotters,  chief  planters,  chief  loaders,  gun  commanders,  gun  pointers 
and  gunners. 

Ready. — At  gun  batteries,  a  signal  given  to  indicate  to  the  gun  pointer  that 
the  piece  is  ready  to  be  fired.  At  mortar  batteries,  a  signal  given  to  the  battery 
commander  that  the  mortars\are  ready  to  be  fired. 

Rear  Slope. — The  rear  slope  to  the  parade  in  rear  of  the  battery. 

Receiving  Table. — The  hoist  table  on  which  ammunition  is  placed  prepara- 
tory to  raising  it  to  the  loading  platform  level. 

Recoil. — The  backward  movement  of  the  gun  on  firing.  It  is  measured  by 
the  distance  which  some  point  on  a  gun  or  carriage  travels  during  recoil.  See 
SECTOR  OF  EXPLOSION. 

Recoil  Cylinder. — The  hydraulic  cylinder  attached  to  the  carriage  for  con- 
trolling the  recoil  of  the  piece. 

Reconnaissance. — An  examination  of  a  territory  or  military  position,  for 
the  purpose  of  obtaining  information  necessary  for  directing  military  operations. 

Reconnaissance  in  Force. — A  demonstration  conducted  in  the  same  general 
manner  as  a  regular  attack.  It  is  made  for  the  purpose  of  drawing  the  fire 
of  the  defense,  discovering  his  strength,  dispositions,  location  of  batteries,  etc. 

Recorder. — An  enlisted  man  stationed  at  each  battle-  and  fire -commander's 


50  THE  SERVICE  OF  COAST  ARTILLERY 

station  who  keeps  an  accurate  written  record  of  all  orders  and  communications 
received  and  transmitted  by  the  battle  or  fire  commander. 

Records  of  Firing. — Data  taken  during  target  practice  or  that  relating  to 
the  gun,  carriage,  conditions  of  loading,  laying,  etc.,  which  would  be  of  value 
in  connection  with  future  firings. 

Rectangular  Target. — See  MATERIAL  TARGET. 

Redoubt. — Usually  a  roughly  constructed  field-work  of  varying  shape  in 
which  all  or  nearly  all  the  angles  are  salient  angles.  They  are  usually  employed 
only  in  positions  in  which  a  small  body  of  troops  desire  to  make  a  very  vigorous 
defense. 

Reference  Numbers. — Arbitrary  numbers  used  to  avoid  "plus"  and 
"minus,"  "right"  and  "left,"  in  data  for  firing.  These  numbers  are  used  on 
the  graduations  of  scales  on  devices  of  the  position-finding  equipment  to  avoid 
liability  of  error  by  the  use  of  one  set  of  numbers  instead  of  two  sets.  Without 
reference  numbers  it  would  be  necessary  to  have  one  set  of  numbers  for  plus, 
and  another  set  for  minus  corrections.  For  example,  if  the  wind  curves  on  the 
range  board  were  numbered  in  both  directions  from  zero,  there  would  be  a 
"plus"  10-mile  wind  curve  and  a  "minus"  10-mile  wind  curve.  In  use  it 
would  be  comparatively  easy  to  make  the  mistake  of  taking  the  plus  10,  instead 
of  the  minus  10.  The  corresponding  reference  numbers,  however,  for  wind 
would  be  60  for  plus  10,  and  40  for  minus  10  (50  being  the  zero).  In  this 
manner  the  liability  of  error  is  minimized. 

Regulations. — Under  the  Constitution  of  the  United  States,  any  rules  for 
the  government  and  regulation  of  the  army  made  by  Congress.  Regulations 
imply  regularity  and  signify  fixed  forms;  a  certain  method,  order  or  precise 
determination  of  functions,  rights  and  duties.  It  embraces  administrative 
service,  system  of  tactics,  and  the  regulation  of  service  in  campaign,  garrison 
and  in  quarters. 

Reinforce. — See  BREECH  REINFORCE. 

Relay. — The  command  given  when  mortars  are  not  to  be  fired  as  laid,  but 
are  to  be  fired  on  the  next  data  furnished. 

Relocation  of  a  Target. — Any  process  whereby  having  the  location  of  a 
target  from  one  point,  its  range  and  azimuth  from  some  other  point  may  be 
determined  without  further  observation. 

Remaining  Velocity. — The  velocity  of  a  projectile  at  any  point  of  the 
trajectory. 

Reserve  Table. — A  table  in  a  sheltered  position  for  reserve  ammunition. 

Resistance  of  the  Air. — The  retarding  effect  of  the  air  on  projectiles 
during  their  flight. 

Restricted  Fire. — See  ORDERS  OF  FIRE. 

Retardation. — The  velocity  a  projectile  loses  in  consequence  of  a  resisting 
medium. 

Retractor. — A  device  for  withdrawing  the  empty  cartridge  shell  rearward 
from  the  bore  of  small -calibe red  guns. 

Reverse  Fire. — Reverse  fire  is  when  the  object  is  fired  at  from  the  rear. 

Ricochet. — The  rebound  of  a  projectile  along  a  surface. 

Rifle. — A  cannon  or  gun  with  the  interior  surface  of  its  bore  grooved  with 
spiral  channels  or  cuts,  thus  giving  the  projectile  a  rotary  motion.  If  the 
interior  surface  of  the  bore  is  smooth,  the  cannon  is  known  as  smooth  bore. 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  51 

Rifling. — The  spiral  grooves  cut  in  the  surface  of  the  bore  of  a  rifle  for  the 
purpose  of  giving  a  rotary  motion  to  the  projectile. 

Rifling,  Twist  in. — See  TWIST  OF  RIFLING. 

Rimbases. — The  masses  of  metal  uniting  the  trunnions  with  the  trunnion 
band. 

Ring  Resistance  Fuse. — A  base  or  point  fuse  used  in  charged  shell  and 
shrapnel.  The  name  is  derived  from  the  manner  in  which  the  firing  pin  is  main- 
tained in  its  normal  or  unarmed  position  by  a  brass  split-ring  spring. 

Roadstead. — A  water  area  where  ships  may  ride  at  anchor  some  distance 
from  the  shore.  An  anchorage  off  shore. 

Rocket. — A  projectile  set  in  motion  by  forces  residing  within  itself,  usually 
used  for  signaling. 

^  Rotating  Band. — The  copper  band  encircling  projectiles  near  their  base 
for  the  purpose  of  giving  them  angular  rotation  in  passing  through  the  rifling 
of  the  bore. 

Rotation. — The  act  of  a  body  turning  on  its  axis. 

Rotation  of  Projectile. — The  act  of  the  projectile  turning  upon  its  axis 
during  the  time  of  flight. 

Round. — A  round  of  ammunition  includes  a  projectile,  charge  and  primer. 
To  fire  one  round  is  to  discharge  one  shot  from  each  gun  of  a  battery. 

Roving  Light. — A  searchlight  intended  to  search  the  battle  area  within  the 
field  not  covered  by  fixed  lights. 

Row. — See  HOOPS. 

Rubber  Impression  of  the  Bore. — An  impression  taken  on  rubber  and 
used  to  determine  the  amount  of  erosion  or  other  irregularities  of  any  portion 
of  the  bore. 

Safety  Lanyard. — A  safety  device  attached  to  seacoast  cannon  consisting 
of  a  lanyard  wound  on  a  drum  working  against  the  action  of  a  spring  and 
attached  to  the  gun.  It  is  so  arranged,  by  means  of  a  ratchet  and  pawl,  that  a 
pull  on  the  firing  lanyard  can  not  be  transmitted  to  the  primer  until  the  gun 
is  in  battery. 

Salvo. — To  fire  all  the  mortars  of  a  pit  or  battery,  or  the  guns  of  a  gun 
battery  simultaneously. 

Salvo  Fire. — Fire  concentrated  from  one  or  more  batteries  against  a  salvo 
point. 

Salvo  Point. — A  point,  the  azimuth  and  range  of  which  are  known  and 
conspicuously  posted  in  the  battery ;  at  which  a  concentrated  fire  from  one  or 
more  batteries  may  be  directed.  Certain  points  in  narrow  channels  are  usually 
selected  as  salvo  points. 

Salvo  Table. — A  table  giving  ranges  and  azimuths  of  salvo  points. 

Scarp. — In  field  fortification  the  wall  of  the  ditch  adjacent  to  the  parapet. 
It  is  always  made  at  as  large  an  angle  as  the  nature  of  the  soil  will  permit, 
the  design  being  to  offer  the  greatest  possible  obstacle  to  the  assailant.  The 
opposite  wall  or  side  is  called  the  counterscarp. 

Scout  Ships. —  Speedy  seagoing  ships  that  patrol  at  a  distance  off  shore, 
to  discover  the  approach  of  the  enemy  and  signal  information  thereof  to  the 
signal  stations  ashore. 

Screw  Box. — The  breech  recess  of  seacoast  cannon. 

Searchlight. — A  high-power  electric  arc  light,  used  for  night  illumination. 


52  THE  SERVICE  OF  COAST  ARTILLERY 

Searchlights  are  classified  as,  Fixed  Lights,  Roving  Lights,  Illuminating  Lights, 
Mine  Field  Lights  and  Battle  Lights.  The  standard  diameters  are  the  60-inch 
and  the  36-inch  lights.  A  few  30-inch  and  24-inch  lights  are  still  in  use. 

Searchlight  Area. — The  area  of  land  or  water  illuminated  by  a  searchlight. 

Searchlight  Observer. — A  member  of  a  searchlight  detachment  equipped 
with  a  night  glass,  stationed  outside  of  fixed  or  roving  lights  at  such  distance 
that  he  can  detect  readily  any  vessel  passing  into  the  beam. 

Searchlight  Officer. — A  coast  artillery  officer  in  charge  of  the  searchlight 
system  covering  a  battle  area,  and  the  manning  party  assigned  thereto.  His 
station  is  at  the  battle-command  station,  or  within  speaking  distance  of  the 
battle  commander.  He  is  responsible  to  him  for  the  condition  of  the  search- 
light material  and  for  the  efficiency  of  the  searchlight  system.  At  night  drill 
and  in  action  he  stands  ready  to  execute  the  orders  of  the  battle  commander 
as  to  searching  the  battle  area.  When  deemed  necessary  by  the  battle  com- 
mander, the  searchlight  officer  may  temporarily  take  charge  of  the  mine-field 
lights.  He  is  responsible  for  the  instruction  of  the  personnel  assigned  to  the 
control  and  operation  of  the  searchlights,  and  by  frequent  inspections  sees  that 
they  are  thoroughly  familiar  with  their  duties  and  the  prescribed  method  of 
searchlight  control.  In  performing  his  duties  from  the  battle  commander's 
station  he  should  be  constantly  on  the  alert  to  see  that  no  vessel  enters  the  battle 
area  without  being  detected  either  by  himself  or  one  of  his  observers,  and  should 
so  direct  the  searchlights  as  to  promptly  pick  up  any  vessel  entering  the 
harbor. 

Searchlight  Operator. — An  enlisted  man  specially  trained  in  the  care  and 
operation  of  searchlights. 

Searchlight  Range. — The  distance  at  which  a  target  can  be  illuminated 
sufficiently  for  identification  and  range-finding  purposes.  The  maximum 
effective  illuminating  range  on  a  clear  night  would  be  approximately  8,000 
yards  for  horizontal-base  range-finding  system;  for  purposes  of  water-lining 
the  target  in  using  the  vertical  base  system  the  range  would  be  approximately 
6,500  yards. 

Searchlight  Tower. — An  elevated  structure  containing  the  searchlight  and 
its  operating  mechanism. 

Seat  of  the  Charge. — The  form  of  that  part  of  the  bore  of  a  firearm  which 
contains  the  charge. 

Secondary  Armament. — The  armament  of  a  coast  artillery  fort  used  to 
defend  the  mine  field;  to  attack  lightly  armored  or  unarmored  ships,  the  upper 
works,  etc.,  and  personnel  of  war  ships  and  defend  the  inner  waters  against 
small  boats  and  landing  parties.  It  includes  3-inch  guns,  small-caliber  guns, 
and  machine  guns  when  on  fixed  mounts. 

Secondary  or  Auxiliary  Power  Plant. — A  reserve  unit  of  power  supply 
usually  located  at  each  battery,  to  furnish  it  with  power  in  case  the  central 
power  plant  or  main  source  of  power  supply  fails  or  is  put  out  of  action. 

Secondary  Station. — A  position-finding  station  furnished  with  an  author- 
ized range-finding  instrument  upon  which  readings  are  taken  simultaneously 
with  those  at  the,  primary  station — if  the  horizontal-base  system  is  used;  or 
upon  which  range  and  azimuth  readings  are  taken  if  the  vertical -base  system 
is  used  and  it  is  desired  to  make  observations  and  obtain  data  taken  from  that 
position. 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  53 

Sector. — A  plane  figure  part  of  a  circle,  inclosed  between  two  radii  and  the 
included  arc. 

Sector  of  Explosion. — At  the  moment  a  cannon  is  fired,  there  is  a  sort  of 
spherical  sector  of  fire  formed  in  front  of  the  piece,  called  sector  of  explosion. 
The  extremity  of  this  sector  presses  against  the  rear  end  of  the  bore  while  the 
external  portion  of  it  terminates  in  the  air,  which  it  compresses  and  drives  in 
every  direction;  the  air  thus  forming  a  support,  the  sector  reacts  with  its  full 
force  upon  the  rear  end  of  the  bore  and  causes  the  recoil  of  the  piece. 

Segment. — A  piece  of  metal  in  the  form  of  the  sector  of  a  circle,  or  part  of 
a  ring. 

Self-Contained  Horizontal  Position  Finder. — A  position-finding  instru- 
ment containing  a  horizontal  base  line  within  itself.  This  base  line  is  from 
eight  to  twenty-five  feet  in  length. 

Semi-Automatic  Machine  Guns. — Rapid-fire  guns  in  which  the  force  of 
recoil  is  used  to  operate  the  breechblock,  but  not  to  load  and  fire  the  piece. 
See  AUTOMATIC  MACHINE  GUNS. 

Separate  Observing  Room. — An  observing  room  which  does  not  adjoin  a 
plotting  room  or  other  observing  room. 

Separate  Plotting  Room. — A  room  in  which  the  plotting  board  is  located 
and  used;  instead  of  being  located  in  the  primary  station. 

Sergeants  Major. — Coast  artillery  corps  non-commissioned  staff  officers 
assigned  to  duty  as  assistants  to  adjutants  in  administrative  functions.  Their 
tactical  duties  are  the  same  as  those  of  regimental  or  battalion  sergeants  major 
of  infantry  and  any  coast  artillery  duty  pertaining  to  their  proper  position. 
Chevrons :  Sergeant  Major,  Senior  Grade.  Three  bars  and  an  arc  of  three  bars. 
Sergeant  Major,  Junior  Grade.  Three  bars  and  an  arc  of  two  bars.  All  to  be 
of  red  cloth. 

Service  Charge. — The  maximum  quantity  of  powder  that  is  perscribed  to 
be  used  in  any  seacoast  cannon. 

Serving  Table. — A  table  for  keeping  a  supply  of  projectiles  convenient  to 
the  breech  during  loading.  It  is  usually  mounted  on  wheels. 

Serving  the  Vent. — The  term  implies  the  removing  of  the  old  primer  from 
the  obturator,  inserting  a  new  one,  adjusting  the  slide  of  the  firing  attachment, 
attaching  the  firing  wire  or  lanyard  and  cleaning  the  vent. 

Set-Back  Point. — A  point  on  the  course  of  a  target  determined  in  a  similar 
manner  as  a  set-forward  point,  but  in  the  opposite  direction. 

Set-Forward  Point. — A  point  on  the  course  of  the  target  in  advance  of  a 
predicted  point,  at  a  distance  from  the  latter  equal  to  the  distance  passed 
over  by  the  target  during  the  time  of  flight  of  the  projectile  for  that  particular 
range. 

Set-Forward  Ruler. — A  celluloid  rule  that  may  be  used  in  the  position - 
finding  system  for  mortars,  to  determine  the  set-forward  point;  It  consists  of 
a  time-of-flight  scale  in  seconds,  a  travel  scale  in  yards  and  a  scale  giving  yards 
of  travel  during  time  of  flight  plus  one  minute.  It  is  arranged  in  the  form  of  a 
slide  rule. 

Shears. — A  form  of  tackle  consisting  of  two  spars  lashed  together  at  one 
point,  forming  an  inverted  V. 

Shell. — A  steel  or  cast  iron  projectile  the  center  of  which  is  hollowed  to  be 
filled  with  the  bursting  charge. 


54  THE  SERVICE  OF  COAST  ARTILLERY 

Shell  Filler. — See  BURSTING  CHARGE. 

Shell  Room. — The  room  for  the  storage  of  projectiles. 

Shell  Tracer. — A  device  attached  to  the  base  of  a  projectile  which  enables 
its  flight  to  be  followed.  In  the  daytime  a  yellow  smoke  is  emitted,  and  at 
night  a  bright  flame. 

Shimose  Powder. — A  high  explosive  of  Japanese  manufacture. 

Shot. — A  term  applied  to  all  solid  projectiles. 

Shot  Chamber. — That  part  of  the  bore  in  which  the  projectile  is  seated. 
It  includes  part  of  the  centering  slope  and  the  rear  portion  of  the  forcing 
cone. 

Shot  Gallery. — A  gallery  or  room  in  the  emplacement  for  the  storage  of 
projectiles. 

Shot  Hoist. — A  device  for  raising  projectiles  from  the  hoist  room  to  the 
loading  or  truck  platform. 

Shot  Hoist  Well. — The  shaft  through  which  the  shot  hoist  operates. 

Shot  Room. — The  room  in  earlier  emplacements  for  the  storage  of  shot. 

Shot  Tongs. — A  mechanical  device  used  to  encircle  the  projectile  at  the 
center  of  gravity  to  facilitate  handling. 

Shrapnel. — A  projectile  composed  of  a  number  of  spherical  balls  inclosed 
in  a  cast  iron  case,  with  a  bursting  charge  in  either  point  or  base  to  scatter 
the  missiles.  The  point  is  armed  with  a  combination  fuse.  It  is  distinguished 
from  shell  by  this  point. 

Sight. — An  instrument  by  which  the  gun  pointer  gives  the  gun  the  proper 
direction  for  firing.  Sights  are  of  two  classes,  open  and  telescopic.  The  former 
consists  of  two  points  which  are  brought  into  line  with  the  target  by  the  unaided 
eye ;  the  latter  uses  the  magnifying  power  of  the  telescope  and  is  the  standard 
sight. 

Sight  Deflection. — The  horizontal  angle  between  the  line  of  sight  and  the 
axis  of  the  piece.  It  is  used  to  correct  for  conditions  of  drift,  wind,  and  move- 
ment of  target  tending  to  cause  deviation. 

Sight  Elevation. — The  elevation  measured  from  the  line  of  sight;  it  is  the 
angle  between  the  line  of  sight  and  the  axis  of  the  bore  when  the  piece  is  pointed. 
It  is  obtained  from  the  angle  of  departure  by  correcting  for  jump. 

Sight  Standard. — A  vertical  steel  post  supporting  the  sight. 

Signal  Rocket. — An  ordinary  skyrocket  used  in  fortress  warfare  and  exer- 
cises, as  a  means  of  communication. 

Signal  Station. — A  station  located  if  practicable  at  a  height  sufficient  to 
give  a  sky  background,  from  which  visual  signals  are  displayed. 

Signs.— See  PAGE  65. 

Six-Inch  Gun. — A  rapid  fire  gun  from  40  to  50  calibers  in  length  and  of 
6-inch  caliber;  mounted  either  upon  disappearing  or  pedestal  carriage. 

Six-Pounder. — A  rapid-fire  gun  of  2.24-inch  caliber.  The  name  denotes 
the  proper  weight  for  the  projectile  of  the  piece. 

Small  Boats. — Launches,  cutters,  gigs  and  j^awls,  used  in  connection  with 
submarine  mine  work,  boat  drill  and  transportation. 

Small-Caliber  Guns. — Guns  of  3-inch  caliber,  6  and  1-pounders. 

Smokeless  Powder. — The  name  given  to  nitro-cellulose  and  nitro-glycerin 
gunpowder. 

Smooth-Bore  Cannon. — See  RIFLE. 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  55 

Sound  Travel. — The  rate  of  travel  of  sound.  Under  normal  conditions  it  is 
approximately  1,150  feet  per  second. 

Specific  Gravity. — The  ratio  of  the  weight  of  a  body  to  the  weight  of  an 
equal  volume  of  water,  in  the  case  of  solids  and  liquids ;  and  to  an  equal  volume 
of  air  in  the  case  of  gases;  taken  as  the  standard  or  unit. 

Sphero-Hexagonal  Powder. — A  black  gunpowder  in  the  form  of  a  small 
ball  with  a  six-sided  ring  around  the  middle. 

Spline. — A  rectangular  piece  fitting  grooves  like  key  seats  in  a  hub  or  shaft, 
so  that  while  the  one  may  slide  endwise  on  the  other,  both  must  revolve  to- 
gether. 

Sponge. — A  swab  used  for  cleaning  the  chamber  and  bore  of  guns  and 
mortars. 

Sprocket  Wheel. — A  toothed  wheel  that  engages  the  links  of  a  chain. 
Spur  Ring. — A  ring  having  radial  teeth  on  the  circumference. 
Spur  Wheel. — A  gear  wheel  having  external  radial  teeth  on  the  circum- 
ference. 

Staff. — For  administrative  and  other  purposes,  the  staff  of  a  coast  artillery 
fort  includes  an  adjutant,  surgeon,  artillery  engineer,  ordnance  officer,  quarter- 
master and  commissary. 
Standards. — See  COLORS. 

Stand  Fast. — A  command  at  which  cannoneers  halt  until  the  previous 
command  is  repeated.  When  one  member  makes  a  mistake  this  command 
is  given  before  the  mistake  is  corrected. 

Star  Gauge. — A  device  for  measuring  the  diameter  of  the  bore  of  cannon. 
It  is  used  during  the  manufacture  and  when  it  is  necessary  to  determine  if  any 
enlargement  of  the  bore  has  t^fcen  place. 

Storage  Magazine. — A  building  provided  for  the  storage  and  preservation 
of  powder  or  explosives;  located  so  as  to  be  protected  from  the  fire  of  the 
enemy. 

Storehouse. — Every  coast  artillery  fort  is  provided  with  one  or  more  store- 
houses for  the  care  and  storage  of  accessory  material. 

Storeroom. — A  room  in  the  emplacement  for  the  storage  of  necessary  ma- 
terial. 

Storm  Flag. — The  national  flag  8-foot  fly  by  4-foot  2-inch  hoist.  Hoisted 
in  stormy  or  windy  weather. 

Strategy. — The  art  of  moving  an  army  in  the  theater  of  operations  with  a 
view  to  placing  it  in  such  a  position,  relative  to  the  enemy,  as  to  increase  the 
probability  of  victory,  increase  the  consequences  of  victory,  or  lessen  the  con- 
sequences of  defeat. 

Strength. — The  number  composing  any  military  body. 
Striking  Angle. — The  angle  which  the  line  of  impact  makes  with  the  hori- 
zontal plane.     It  is  equal  to  the  angular  depression  of  the  point  of  impact  plus 
the  angle  between  the  line  of  impact  and  the  line  of  shot. 
Striking  Energy. — See  ENERGY  OF  PROJECTILE. 

Striking  Velocity. — The  velocity  of  the  projectile  at  the  point  of  impact. 
vSubcaliber  Platform. — A  steel  platform  attached  to  the  breech  of  large- 
caliber  guns  upon  which  the  breech  detail  stands  to  load  the  subcaliber  tube 
during  practice.     After  the  platform  is  attached  the  piece  is  placed  in  battery. 
At  batteries  not  equipped  with  the  prescribed  pattern  a  platform  of  wood  is 


56  THE  SERVICE  OF  COAST  ARTILLERY 

constructed  by  lashing  heavy  planks  to  the  sighting  platforms  so  that  they 
will  extend  about  six  feet  in  rear  of  the  breech;  flooring  is  then  nailed  to  the 
planks. 

Subcaliber  Quadrant  Scale. — Scales  used  on  gun  carriages  to  set  the  piece 
in  elevation  during  subcaliber  practice  in  place  of  the  regular  service  scale. 
They  are  constructed  for  ranges  in  yards  corrected  for  height  of  site  and 
curvature,  and  are  used  in  the  same  manner  as  the  regular  quadrant  scale. 

Subcaliber  Tube. — A  small  caliber  gun  which  is  seated  in  the  bore  of  a  gun 
of  larger  caliber;  used  for  target  practice  with  ammunition  of  smaller  charges 
and  caliber  than  the  gun  in  which  it  is  used.  In  rapid  fire  guns  this  device  is 
contained  in  a  dummy  projectile.  They  are  classified  as  30/100-inch  caliber, 
1-pounder,  and  18-pounder. 

Submarine  Boat. — Small  boats  capable  of  maneuvering  under  the  surface 
of  the  water.  There  are  two  types,  namely:  Holland  and  Lake.  On  the  sur- 
face they  have  the  appearance  of  a  small  monitor;  when  submerged  only  the 
conning  tower,  hood  and  sighting  apparatus  are  visible;  when  completely 
submerged  only  the  signal  mast  is  visible  and  this  only  when  desired  or  when 
submergence  is  not  great.  They  fire  torpedoes  from  one  or  two  tubes  in  all 
three  positions.  Average  length  60  to  70  feet;  beam  11  to  14  feet;  speed 
10  to  12  knots;  partially  submerged  8  to  10  knots;  submerged  8  knots. 

Submarine  Boat  Signal  Flag. — A  flag  of  bunting  showing  a  black  fish  on 
a  white  surface  and  surrounded  by  a  red  border.  This  flag  is  flown  from  the 
tender  or  parent  vessel  attending  submarine  boats.  Its  function  is  to  notify 
shipping  that  a  submarine  boat  is  below  the  surface  of  the  water  in  the 
vicinity. 

Submarine  Defense  Equipment. — Submarine  defense  equipment  includes 
submarine  mines,  mobile  torpedoes,  obstructions  and  all  material  pertaining 
to  the  placing  and  service  of  these  means  of  defense. 

Submarine  Defenses. — Submarine  defenses  include  submarine  mines, 
mobile  torpedoes,  marine  obstructions  and  submarine  boats. 

Submarine  Mine.— A  submerged  stationary  torpedo  consisting  of  an  explo- 
sive charge  and  firing  device,  inclosed  in  a  water-tight  steel  case,  to  be  fixed 
in  position  in  a  channel  which  it  is  desired  to  close  against  the  passage  of  an 
enemy's  vessels.  They  are  classified  as  mechanical,  when  they  are  exploded  by 
means  of  a  firing  device ;  and  electrical,  when  exploded  by  electricity. 

Superior  Slope. — The  top  slope  of  a  parapet  or  traverse. 

Supplementary  Station. — An  auxiliary  base-line  station  used  to  furnish 
data  in  place  of  the  secondary  station  in  case  said  station  is  put  out  of  action, 
or  to  furnish  data  over  a  field  of  fire  not  covered  by  the  secondary  station. 

Surface. — The  exterior  part  of  anything  that  has  length  and  breadth;  the 
outside,  as  the  surface  of  the  earth. 

Surveyor's  Transit. — An  angle-measuring  instrument  similar  in  its  essential 
parts  to  the  azimuth  instrument,  but  of  more  delicate  and  complicated  design. 
It  may  be  used  to  measure  both  horizontal  and  vertical  angles  as  well  as  give 
the  magnetic  bearing.  Its  principal  parts  are  shown  by  name  and  detail  in 
chapter  on  Fire-Control  Instruments,  etc. 

Swell  of  the  Muzzle. — The  enlargement  of  the  exterior  of  the  gun  at  the 
muzzle. 

Symbol  Charts. — See  VESSEL  CHARTS. 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  57 

Tackle. — A  purchase  formed  by  reeving  a  rope  through  two  or  more  blocks, 
for  the  purpose  of  hoisting. 

Tactical  Chain  of  Artillery  Command. — The  combined  tactical  units  of 
seacoast  defense. 

Tactical  Command. — Command  at  drill  and  during  action. 

Tactical  Responsibility. — Responsibility  for  all  matters  affecting  the  effi- 
ciency of  a  tactical  command. 

Tactics. — The  art  of  drilling  troops,  and  of  handling  and  maneuvering  them 
in  the  presence  of  the  enemy.  See  BATTLE  TACTICS. 

Take  Cover. — A  command  which  can  be  given  at  any  time,  at  which  all 
numbers  not  designated  to  remain  at  their  post  move  at  a  run  to  some  desig- 
nated place  under  cover.  As  a  rule  this  command  is  given  in  mortar  batteries 
only. 

Tangent. — A  line  lying  in  the  plane  of  a  circle  and  touching  the  circumference 
at  one  point. 

Tangent  of  an  Arc. — That  part  of  the  tangent  which,  touching  the  arc  at 
one  extremity,  is  limited  by  the  line  passing  through  the  other  extremity  and  the 
center  of  the  circle. 

Tangential  Force. — A  force  which  acts  on  a  moving  body  in  the  direction 
of  the  tangent  to  the  path  of  the  body,  its  effect  being  to  increase  or  diminish 
the  velocity;  distinguished  from  a  normal  force,  which  acts  at  right  angles  to  the 
tangent  and  changes  the  direction  of  the  motion  without  changing  the  velocity. 
A  ricochet  shot  or  a  foul  tip  in  base  ball,  are  examples  of  applied  tangential 
force. 

Targ. — The  piece  of  metal  used  to  indicate  the  intersection  of  the  arms  on 
the  plotting  board. 

Target. — The  object  at  which  guns  or  mortars  are  pointed ;  as  a  boat,  ship 
or  other  object,  whether  stationary  or  moving. 

Target  or  Vessel  Tracking. — The  process  whereby  successive  positions  of  a 
moving  target  are  plotted  on  a  chart  or  plotting  board.  It  includes  the  observa- 
tions made  by  the  observers  at  the  position-finding  instruments,  the  plotting 
of  the  results  of  these  observations  on  a  plotting  board  at  the  same  time  tracing 
thereon  the  plotted  track  of  the  course  of  the  target. 

Telautograph. — An  electro-mechanical  instrument  by  means  of  which  the 
movement  of  an  attached  pencil  used  by  a  person  in  writing  at  one  end  of  the 
circuit,  will  automatically  trace  or  reproduce  the  characters,  as  written,  at  the 
other  end. 

Telephone. — An  instrument  by  means  of  which  a  sound  produced  at  one  end 
of  a  wire  is  reproduced  at  the  other  end.  There  are  two  types  in  use — the 
Service  Telephone,  used  in  temporary  installations;  and  the  Composite  Artillery 
Type  Telephone,  used  in  permanent  installations. 

Telescopic  Sight. — A  combination  sight  and  telescope  used  for  the  aiming 
of  guns  at  ranges  greater  than  an  object  could  be  distinguished  with  the  naked 
eye.  The  advantage  of  telescopic  sights  are  the  increased  power  of  vision ;  large 
decrease  in  personal  error ;  and  the  great  facility  and  accuracy  of  aiming  a  gun 
at  the  greater  ranges.  See  SIGHT. 

Ten-Inch  Gun. — A  seacoast  cannon  usually  35  to  40  calibers  long  and  of 
10-inch  caliber. 

Terrain. — The  ground,  its  configuration  and  natural  and  artificial  diversifi- 


58  THE  SERVICE  OF  COAST  ARTILLERY 

cation.  The  topographical  character  of  the  country,  region  or  tract,  as  viewed 
from  a  military  standpoint. 

Thawing  Explosives. — See  MELTING  AND  THAWING  EXPLOSIVES. 

Theater  of  Operations. — All  the  territory  an  army  may  desire  to  invade, 
and  all  that  it  may  be  necessary  to  defend. 

Theoretical  Range  or  Range  of  Ballistic  Tables. — The  horizontal  distance 
from  the  muzzle  of  the  gun  to  that  point  of  the  descending  branch  of  the  tra- 
jectory, called  the  point  of  fall,  which  is  at  the  level  of  the  muzzle  of  the  gun. 
This  definition  of  the  theoretical  range  is  strictly  accurate  and  is  conveniently 
applicable  in  using  quadrant  elevation,  as  with  mortar  fire;  but  in  using  sight 
elevation  it  is  more  convenient,  assuming  the  principle  of  the  rigidity  of  the 
trajectory,  to  define  the  theoretical  range  as  the  distance  from  the  muzzle  of 
the  gun  to  the  point  of  intersection  of  the  trajectory  with  the  line  from  the  muz- 
zle to  the  target,  the  distance  being  measured  along  this  line.  The  point  of 
intersection  is  called  the  point  of  fall. 

Theory  of  Probability. — See  PROBABILITY  OF  ERROR. 

Thermometer. — An  instrument  for  measuring  temperature. 

Three-Inch  Gun. — A  rapid-fire  gun  40  to  50  calibers  long  and  of  3-inch 
caliber.  Commonly  called  "Fifteen  Pounder." 

Throttling  Bar. — A  bar  in  the  recoil  cylinder  to  regulate  the  size  of  the 
orifice  through  which  the  oil  escapes  from  one  side  of  the  piston  head  to  the 
other. 

T-I  Bell. — See  TIME-INTERVAL  BELL. 

Tide  Gauge. — A  mechanical  device  used  to  register  the  height  of 
tide  in  feet  and  hundredths  above  the  datum  plane  (mean  low  water). 
It  consists  essentially  of  a  float  connected  with  an  automatic  registering 
device. 

Tide  Indicator. — A  device  operated  electrically  to  indicate  height  of  tide 
in  all  primary  stations.  It  is  operated  by  a  controller  located  in  the  tide 
station. 

Tide  Station. — A  station  at  which  periodical  readings  of  height  of  tide  are 
made,  recorded  and  sent  to  the  various  primary  stations  throughout  the  fire- 
control  command. 

Time  Fuse. — A  fuse  which  ignites  the  bursting  charge  at  some  fixed  time 
after  the  projectile  leaves  the  muzzle. 

Time-Interval  Bell. — A  bell  with  electrical  attachment,  located  in  all  em- 
placements, primary  and  secondary  stations,  for  the  purpose  of  sounding 
simultaneous  signals  to  indicate  the  observing  interval.  Commonly  called 
"T-I  Bell." 

Time  of  Flight  Scale. — A  scale  giving  the  time  of  flight  in  seconds  for  any 
particular  muzzle  velocity  and  projectile,  for  ranges  from  one  to  twelve  thousand 
yards.  The  term  is  also  applied  to  the  travel  of  the  vessel  in  yards  during  the 
time  of  flight  for  any  projectile  at  the  range  considered.  In  the  case  of  mortars, 
the  term  is  applied  to  the  time  of  flight  scale  on  the  predicter,  which  gives  the 
yards  of  travel  during  the  time  of  flight  plus  one  minute. 

Time-Interval  Recorder. — The  ordinary  stop-watch. 

Time-Range  Board. — A  board  to  show  range  of  target  from  battery  at  any 
instant.  It  is  placed  on  the  emplacement  wall  and  is  operated  on  data  from 
the  plotting  room. 


DEFINITIONS,  ABBREVIATIONS  AND   SIGNS  59 

Tool  Room. — A  room  in  the  battery  for  the  storage  of  necessary  tools  and 
implements. 

Torpedo. — An  explosive  device  belonging  to  either  of  two  distinct  classes 
of  submarine  destructive  agents  intended  for  use  in  time  of  war.  The  torpedo 
proper  to  which  the  name  properly  applies,  is  a  cigar-shaped  vessel  designed 
for  offensive  subwater  attack  against  the  enemy's  ships.  The  other  class  to 
which  the  name  is  applied  is  a  purely  defensive  weapon  and  is  more  correctly 
termed  submarine  mine.  It  consists  of  an  explosive  charge  inclosed  in  a  water- 
tight case  which  is  submerged  and  anchored  in  channels,  etc.  See  MOBILE 
TORPEDO. 

Torpedo  Boats. — Long,  low  and  narrow  war  vessels  modeled  after  torpedo- 
boat  destroyers.  They  have  no  armor  protection.  Average  speed,  22  to  29 
knots,  tonnage  103  to  107  tons.  Armament,  three  to  five  one-pounders  and 
three  torpedo  tubes.  They  are  nothing  more  than  metal  shells  three-eighths 
of  an  inch  thick.  They  are  necessary  for  each  important  fortified  point,  to  meet 
and  repel  attacks  made  by  the  enemy's  torpedo  boats  on  the  shipping  at  anchor 
inside  the  line  of  fixed  defenses;  to  attack  large  ships  of  the  enemy  when 
opportunity  offers,  and  protect  the  mine  fields. 

Torpedoboat  Destroyers. — Long,  low  and  narrow  war  vessels,  with  high 
bow  and  higher  freeboard  forward  than  aft.  They  have  no  armor  protection. 
Average  speed  29  to  31  knots,  tonnage  275  to  740  tons.  Armament,  six  to 
eight  14  and  6-pounders,  and  two  torpedo  tubes.  Their  functions  in  connec- 
tion with  coast  defense  cover  the  same  general  duties  as  those  of  torbedo  boats, 
except  that  they  have  better  seagoing  qualities. 

Torpedo-Detonating  Pierce  Fuse. — A  delayed  action  fuse  used  to  detonate 
high-explosive  bursting  charges  in  mortar  projectiles. 

Torpedo  Shell. — A  deck-piercing  shell  with  an  unusually  large  explosive 
cavity,  fired  from  mortars  for  the  purpose  of  carrying  a  large  explosive  charge 
to  the  decks  of  war  vessels. 

Towing  Target. — Any  target  which  is  capable  of  being  towed  behind  a 
boat, 

Tracking. — The  method  employed  in  locating  the  course  of  a  vessel  on  the 
plotting  board,  by  taking  simultaneous  readings  at  the  two  base-end  stations 
at  regular  intervals,  and  plotting  the  location  of  the  target  at  the  instant  of  eac  h 
observation.  See  TARGET  OR  VESSEL  TRACKING. 

Trajectory. — The  curve  described  by  the  center  of  gravity  of  the  projectile. 
The  path  of  a  projectile  in  its  flight  through  the  air  from  the  muzzle  of  the 
gun  to  the  point  of  impact. 

Transit  Instrument. — See  SURVEYOR'S  TRANSIT. 

Travel  of  Projectile. — The  distance  from  the  base  of  a  projectile  in  its  seat 
in  the  bore  to  the  muzzle  of  the  gun. 

Travel  of  Target. — The  distance  passed  over  by  the  target  in  the  time  of 
flight.  It  is  also  used  to  express  the  distance  passed  over  by  the  target  in  an 
observing  interval. 

Traverse. — In  fortification,  the  structure  perpendicular  or  oblique  to  the 
parapet  wall,  protecting  the  armament  and  personnel  from  flank  fire.  In  gun- 
nery, a  term  used  to  indicate  the  horizontal  travel  of  the  piece  either  to  the 
right  or  left, 

Traverse  Slope  or  Wall. — The  side  slope  or  wall  of  the  traverse. 


60  THE  SERVICE  OF  COAST  ARTILLERY 

Traversing  Indicator. — A  device  used  by  gun  pointers  to  control  the 
traversing  of  a  gun  without  command. 

Tray. — See  LOADING  TRAY. 

Trial  Shots. — Shots  fired  before  practice  or  action  to  determine,  for  guns, 
the  muzzle  velocity  to  be  used;  for  mortars — the  range  and  deflection  correc- 
tions to  be  applied. 

Trinitrotoluol. — A  detonating  and  disruptive  explosive  of  high  order  used 
as  a  base  for  shell  fillers. 

Tripping. — The  act  of  releasing  the  counterweights  of  a  disappearing  car- 
riage, thereby  carrying  the  piece  in  battery,  i.e.,  moving  the  top  carriage 
forward  so  that  the  muzzle  extends  over  the  parapet. 

Trolley. — A  mechanical  device  for  transporting  projectiles  on  horizontally 
suspended  tracks. 

Truck. — See  AMMUNITION  TRUCK. 

Truck  Platform. — If  the  ammunition  trucks  run  on  a  different  surface 
from  that  of  the  loading  platform,  this  surface  is  called  the  "truck  plat- 
form." 

Truck  Recess. — The  spaces  built  in  the  parapet  wall  for  the  storage  of 
ammunition  trucks. 

Trunnion  Band  or  Hoop. — The  hoop  around  a  cannon,  of  which  the 
trunnions  form  a  part,  located  at  about  the  center  of  gravity. 

Trunnion-Sight  Bracket. — A  bracket  attached  to  the  right  trunnion  of  a 
gun,  which  may  be  used  for  holding  the  telescopic  sights. 

Trunnions. — Trunnions  are  cylinders  designed  to  rest  in  bearing  surfaces 
of  carriages,  called  "trunnion  beds,"  their  axis  being  perpendicular  to  the  axis 
of  the  bore,  and  ordinarily  in  the  same  plane;  they  connect  the  gun  with  the 
carriage  and  transmit  the  force  of  recoil  from  one  to  the  other. 

Twelve-Inch  Gun. — A  seacoast  cannon  usually  thirty-five  to  forty  calibers 
in  length  and  of  12-inch  caliber. 

Twelve-Inch  Mortar. — A  seacoast  mortar  usually  nine  to  ten  calibers  in 
length  and  of  12-inch  caliber. 

Twist  of  Rifling. — The  inclination  of  the  grooves  to  the  axis  of  the  gun  at 
any  point  in  the  bore.  The  twist  is  said  to  be  increasing  when  the  inclination 
gradually  increases  from  the  breech  to  the  muzzle;  uniform  when  the  inclina- 
tion is  constant.  Twist  is  generally  expressed  in  terms  per  caliber,  viz. :  one 
turn  in  40  calibers,  meaning  that  the  projectile  makes  one  complete  revolution 
in  passing  over  a  length  of  the  bore  equal  to  40  calibers. 

Tube.^The  inner  wall  of  the  bore  of  a  built-up  gun  extending  usually  from 
the  breech  to  the  muzzle,  ordinarily  made  one  piece. 

Tug  Observer. — A  coast  artillery  officer  detailed  by  the  post  commander 
for  duty  aboard  a  tug  engaged  in  towing  and  maneuvering  targets  during 
subcaliber  or  service  target  practice.  His  principal  duties  are  to  supervise 
the  use  of  the  camera  or  range  rake  in  taking  range  deviations  (overs  and 
shorts) . 

Tug  Officer. — A  coast  artillery  officer  in  charge  of  a  tug  engaged  in  towing 
and  maneuvering  targets  during  subcaliber  or  service  target  practice.  The 
actual  maneuvering  of  targets  from  the  tug  is  under  the  supervision  of  the 
master  of  the  tug,  subject  to  the  orders  of  the  tug  officer. 

Union  Jack. — A  flag  of  bunting  consisting  of  46  white  stars,  in  six  rows, 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  61 

the  first,  third,  fourth  and  sixth  rows  to  have  8  stars,  and  the  second  and  fifth 
rows  7  stars  each,  in  a  blue  field. 

Unit. — A  military  body  acting  together.  Military  units  are  divided  into 
two  classes,  i.e.,  administrative  units,  which  include  those  necessary  for  the 
proper  care,  housing,  clothing,  feeding,  instruction,  disciplining  and  keeping  of 
military  records ;  and  tactical  units,  which  are  organized  and  equipped  with  a 
view  of  their  highest  efficiency  in  action. 

Unrestricted  Fire. — See  ORDERS  OF  FIRE. 

Vedette. — A  mounted  sentinel. 

Velocity. — The  common  term  used  to  denote  speed,  or  rate  of  motion. 
Velocities  with  guns  vary  from  2,000  to  3,000  feet  per  second,  with  mortars 
from  550  to  1,300  feet  per  second. 

Velocity  of  Combustion. — The  rate  of  burning  of  a  powder  grain. 

Velocity  of  Rotation. — The  rate  of  motion  of  a  body  around  its  axis,  as  a 
wheel,  as  distinguished  from  progressive  motion  of  a  body  in  the  direction  of  a 
distant  point.  In  gunnery  it  is  the  rate  of  motion  of  the  projectile  at  any 
point  in  the  trajectory  around  its  longer  axis. 

Velocity  of  Translation. — The  rate  of  travel  of  the  projectile  in  the  direction 
of  its  flight. 

Vent. — A  small  channel  leading  from  the  exterior  to  the  powder  chamber 
for  ignition  of  the  powder  charge. 

Ventilators. — The  shafts  or  flues  with  movable  covers  for  ventilation, 
leading  from  interior  galleries  or  air  spaces  and  opening  through  the  superior 
slope. 

Vernier. — A  small  auxiliary  scale  enabling  the  measurement  of  hundredths 
(or  minutes  and  seconds)  in  connection  with  the  main  scale. 

Vertical. — Perpendicular  to  the  plane  of  the  horizon.  The  line  of  direction 
through  the  center  of  the  earth  which  is  taken  up  by  the  plumb  bob  when 
freely  suspended  by  a  line  and  allowed  to  come  to  rest. 

Vertical  Angle. — An  angle  whose  sides  lie  wholly  in  the  vertical  plane. 

Vertical  Base  System. — The  system  of  range  finding  in  which  the  azimuth 
and  range  are  determined  by  one  position-finding  instrument,  located  at  either 
of  the  (horizontal)  base-end  stations.  The  base  line  in  this  system  extends 
from  the  horizontal  axis  of  the  trunnions  of  the  instrument  vertically  to  mean 
low-water  level.  The  vertical  base  feature  of  the  position-finding  instrument 
is  used  exclusively  in  this  system. 

Vessel  Charts. — Charts,  usually  blue  prints,  used  in  the  identification  of 
targets.  These  charts  consist  of  a  system  of  vessel  symbols  giving  a  classifica- 
tion in  outline  of  warships  in  connection  with  funnels  and  masts. 

Vertical  Plane. — Any  plane  which  passes  through  a  vertical  line  or  con- 
tains the  line  of  the  plumb  bob  when  freely  suspended  by  a  line  and  allowed  to 
come  to  rest. 

Vertex  of  an  Angle. — The  point  at  which  the  sides  of  an  angle  meet. 

Vessel  Tracking.  — See  TARGET  OR  VESSEL  TRACKING. 

Vickers-Maxim  Gun. — A  rapid-fire  gun  of  1.457-inch  caliber,  usually  called 
"one-pounder." 

Water  Front. — That  portion  of  the  defenses  bearing  upon  the  navigable 
water  areas  that  may  be  open  to  an  enemy. 

Wheeled  Mount. — See  CARRIAGE  or  MOUNT. 


62  THE  SERVICE  OF  COAST  ARTILLERY 

Winch. — A  machine  operated  by  steam  or  other  motive  power,  used  on 
mine  planters  for  raising  anchors  and  other  heavy  weights.  It  consists  of  a 
drum,  crank  and  the  necessary  gearing  arranged  for  gaining  power. 

Wind-Component  Indicator. — A  device  used  in  primary  stations  of  the 
fire-control  system  to  indicate  to  the  operators  of  the  range  and  deflection 
boards,  the  reference  numbers  corresponding  to  the  range  and  deflection  com- 
ponents of  the  wind  as  sent  from  the  meteorological  station. 

Wind  Vane. — A  device  pertaining  to  the  meteorological  station,  which 
indicates  the  azimuth  of  the  wind. 

Wireless  Station. — A  station  located  within  the  fortification  in  which  wire- 
less telegraph  apparatus  is  installed. 

Worm. — A  short  threaded  portion  of  a  shaft,  constituting  an  endless  screwr 
formed  to  mesh  with  a  gear  wheel. 

Xylol. — A  colorless  oily  inflammable  liquid,  used  in  the  bath  for  making 
the  135-degree  stability  test  of  nitro-cellulose  powder. 

Zero. — The  point  from  which  instruments,  etc.,  are  graduated.  In  com- 
municating numerals  it  is  a  word  used  to  indicate  a  cipher  or  naught.  For 
example,  340.30,  would  be  expressed:  "Three-four-zero-point-three-zero." 

Zone  Energy. — A  term  denoting  the  relative  armor-piercing  power  of 
different  guns.  It  is  estimated  by  the  number  of  foot-tons  per  inch  of  the 
shot  circumference.  At  the  muzzle  this  power  is  a  maximum,  but  owing  to 
the  resistance  of  the  air  it  gradually  diminishes  during  flight. 

Zone  Mort. — A  French  military  expression  denoting  the  space  in  which 
the  projectile  has  lost  its  strength,  or  is  spent. 

Zone  of  Fire. — A  term  synonymous  with  specified  fire  areas.  In  mortar 
firing  it  is  the  particular  area  in  which  projectiles  fall  for  a  given  charge  of 
powder  when  the  elevation  is  varied  between  minimum  and  maximum.  The 
several  zones  of  fire  for  the  12-inch  steel  mortars  are,  1st  Zone,  2,210  to  2,970; 
2d  Zone,  2,600  to  3,431 ;  3d  Zone,  3,070  to  4,030;  4th  Zone,  3,631  to  4,800; 
5th  Zone,  4,429  to  5,940;  6th  Zone,  5,520  to  7,476;  7th  Zone,  7,027  to  9,250; 
8th  Zone,  8,758  to  12,019  yards. 

In  the  case  of  rifle  fire  the  defensive  area  between  the  guns  and  4,000  yards 
range,  is  known  as  the  "inner  defense  zone/'  between  4,000  and  8,000  yards 
range,  as  the  "middle  defense  zone;"  and  between  8,000  and  12,000  yards 
range,  as  the  "outer  defense  zone." 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  63 


ABBREVIATIONS. 

A.R.F All-round  fire. 

A.P Armor-piercing  (shot  or  shell). 

B' Primary  station  of  a  battery. 

B" Secondary  station  of  a  battery. 

B'" Supplementary  station  of  a  battery. 

BC Battery  commander's  station. 

B.C Battery  commander. 

B.L.L Bolt-locking  lug. 

B.L.R Breech-loading  rifle. 

C Battle  commander's  station. 

C.A.C Coast  artillery  corps. 

C.A.D Coast  artillery  district. 

C.A.D.R Coast  artillery  drill  regulations. 

C.E Corps  of  engineers. 

C.I Cast-iron  (shot  or  shell). 

D.C Disappearing  carriage. 

D.C.L.F Disappearing  carriage  limited  fire. 

D.P Deck  piercing. 

D.P.F Depression-position  finder. 

D.R Drill  regulations. 

D-S Driggs-Schroeder  or  Driggs-Seabury. 

E Emergency  station. 

F' Primary  station  of  a  fire  command. 

F" Secondary  station  of  a  fire  command. 

F"' Supplementary  station  of  a  fire  command. 

F.A Frankford  Arsenal;  field  artillery. 

F.C Fire  commander. 

f.s Feet  per  second. 

H.P.F Horizontal  position  finder. 

I Illuminating  light. 

I. V Initial  velocity. 

M.  .  .  .  . Mortar;  model. 

M' Primary  station  of  a  mine  command. 

M" Secondary  station  of  a  mine  command. 

M"' Supplementary  station  of  a  mine  command. 

M'-M' Double  primary  station  of  a  mine  command. 

M"-M" Double  secondary  station  of  a  mine  command, 

Met Meteorological  station. 

Mi Mark  one,  meaning,  first  modification. 

mi Miles. 

M.L.R Muzzle-loading  rifle. 

M.V Muzzle  velocity. 

O Separate  observing  room. 

O.D Ordnance  department. 

P Separate  plotting  room. 

P.  .  .  .  Pressure. 


64  THE  SERVICE  OF  COAST  ARTILLERY 

P.S.B Post  telephone  switchboard. 

Proj Projectile. 

R Rifle. 

R.F Rapid  fire. 

S Searchlight. 

S.E Striking  Energy. 

SS   Signal  station. 

S.V Striking  velocity. 

Sub.  Cal Sub-caliber. 

T  Tide  station. 

T Torpedo. 

T.D Torpedo-detonating  (Pierce  fuse). 

T.  I.  Bell Time-interval  bell. 

V Velocity. 

W Weight. 

W.D War  department. 

WS Wireless  station. 

Q.F Quick-firing. 

Q.M.D Quartermaster  department. 

W.&  S Warner  &  Swasey. 


DEFINITIONS,  ABBREVIATIONS  AND  SIGNS  65 

SIGNS. 

Primary  Station  of  a  Battery (o) 

Secondary  Station  of  a  Battery I  g"| 

Supplementary  Srat/on  of  a  Battery I  g'"| 

Battery  Commander's  Station (BCi 

Battle Commander's  Statioh T ... (^CB 

Emergancy Station  ofa  Battery. C^\ 

Primary  Station  of  a  F/re  Command (F^ 

Secondary  Station  of  a  Fire  Command. I  p"  I 

Supplementary  Station  of  a  F/re  Command I  p'"j 

Illuminating  Light I    |   I 

Primary  Station  of  a  Mine  Command. . Mvn 


Secondary  Station  of  a  Mine  Command  ___________________________  |M"| 

Supplementary  Station  of  a  M/ne  Command.  _____________________  \M"f\ 

Doub/e  Primary  Station  ofaMine  Command.  _______________________  (M^Cm 

Double  Secondary  Station  of  a  Mine  Command.  __________________  |M"-|-M"| 

Meteorological  Station  ______________________________________________  |[7Tj| 

Separate  Observing  Room  ______________________  ,  ____________________  ^0^ 

Separate  P/ott/ng  Room  ______________________________________  ^  _______  /^\ 

Post  Telephone  Switchboard  ______  ^  ____________________________  pv/j 

Searchlight-  _____________________________________  _________  [sj 

Searchlight  36  inch.  ___________________  __  _______  \36\ 

Searchlight  6O  inch  _______  _______________________  160) 

Tide  Station.  ______________________  !  ______________________  Il 


Signal  'Station  ________________________________  _  _______________  ||  -     - 

Wire/ess  Station,...  ______ 


CHAPTER   II 
THEORY  AND  PRINCIPLES  OF  COAST  DEFENSE 

THE  fundamental  object  of  coast  defense — in  the  general  accepta- 
tion of  the  term — is  to  afford  suitable  means  of  protection  to  the  coast 
line  with  a  view  to  resisting  invasion  by  an  enemy.  Harbor  defense 
is  that  branch  of  coast  defense  which  has  for  its  object  the  protection 
of  important  harbors  and  cities  situated  on  or  near  the  sea,  as  well  as 
the  securing  of  adequate  anchorages  and  bases  for  the  navy  in  time  of 
hostilities.  Thus  coast  defense  in  the  largest  sense  becomes  not  only 
protective  in  its  strength  but  a  productive  contributor  to  the  nation's 
ability  to  carry  on  war  beyond  her  coast  line. 

It  is  not  practicable  to  fortify  the  entire  extent  of  the  coast  in 
such  a  manner  that  an  enemy  in  command  of  the  sea  could  not  land 
upon  some  portion  of  it.  The  cost  of  such  an  undertaking  would 
be  excessive,  and  the  maintenance  and  number  of  men  required  as  a 
personnel  would  make  it  prohibitive.  It  is  essential,  however,  that 
certain  selected  points  shall  be  permanently  fortified,  and  in  their 
selection  the  following  conditions  should  be  considered: 

First. — The  value  of  the  property  accumulated  at  such  points  and 
the  importance  of  this  property  to  the  function  of  commercial  pursuits, 
as  well  as  the  value  of  such  points  to  the  enemy. 

Second. — The  importance  of  defending  convenient,  well-protected 
and  sheltered  harbors  or  anchorages  for  naval  and  military  bases,  and 
preventing  the  occupation  of  such  points  by  the  enemy. 

The  means  of  defending  the  coast  line  are  divided  into  two  general 
units.  The  first  of  these  comprehends  the  fortifications  manned  by  the 
Coast  Artillery  troops  proper;  which  include  the  personnel  of  the 
Regular  Coast  Artillery  Corps,  assisted  by  the  Coast  Artillery  Reserve. 
The  fortifications  are  protected  against  attack  of  small  landing  parties, 
by  infantry  troops,  called  Coast  Artillery  Supports. 

The  second  general  unit  comprehends  the  troops  necessary  to  pro- 
tect unfortified  portions  of  the  coast  line. 

The  functions  of  the  navy  are  not  within  the  scope  of  this  work. 

66 


THEORY  AND  PRINCIPLES  OF  COAST  DEFENSE  67 

However,  the  navy  is  prepared,  by  reason  of  its  mobility,  to  carry  on 
offensive  warfare.  The  means  of  protecting  unfortified  portions  of  the 
coast  line  are  also  tactically  offensive  in  their  action,  while  the  harbor 
defenses  or  fortifications  are  purely  defensive.  Ships  of  the  line  and 
smaller  craft  such  as  monitors,  scout  ships,  torpedo  boats  and  submarine 
boats  may  be  attached  to  the  land  forts  and  assigned  as  floating 
defenses  unless  it  is  desirable  that  they  be  otherwise  engaged.  Their 
functions  consist  of  assisting  the  artillery  defense  at  any  point  or  points 
required  in  the  plans  of  defense. 

The  functions  of  the  coast  artillery  troops  proper,  are  the  manning 
and  operation  of  the  armament  of  coast  forts,  the  control  of  'the  sub- 
marine defense  and  the  location  of  such  marine  obstructions  as  may 
be  found  necessary  at  the  entrance  of  harbors. 

The  coast  artillery  supports  are  charged  with  the  duty  of  flank  and 
land  front  security  and  information,  as  well  as  the  protection  of  the 
fortifications  against  attack  by  small  parties  of  the  enemy  landed  close 
to  their  flanks,  thus  making  sure  that  the  coast  artillery  troops  proper 
shall  not  be  harassed  or  annoyed  in  the  performance  of  their  proper 
duties. 

The  function  of  the  coast  guard  is  the  protection  of  unfortified 
portions  of  the  coast  line  lying  adjacent  to  fortifications,  such  protec- 
tion being  sufficient  to  resist  the  most  powerful  landing  parties  of  the 
enemy  and  prevent  the  capture  of  the  fortifications,  together  with  the 
cities  and  harbors  they  defend.  In  this  duty  they  will  be  supported 
by  field  armies. 

THE    THEORY    OF    DEFENSE 

Before  entering  into  a  discussion  of  the  various  phases  of  fortress 
warfare  it  is  appropriate  to  weigh  the  efficacy  of  fire  to  be  delivered 
by  the  two  combatants.  It  is  evident  that  fire  from  ships  cannot  be 
delivered  at  as  great  an  accurate  range  as  that  available  to  the  guns  of 
coast  fortifications.  The  enemy  is  at  a  disadvantge  in  not  being  able 
to  use  the  higher  elevations  with  any  degree  of  accuracy,  which  neces- 
sarily reduces  his  maximum  effective  range.  In  this  connection  atten- 
tion may  be  called  to  the  fact  that  the  turret  openings  in  the  later 
types  of  battleships  allow  a  twenty-degree  elevation,  which,  with  a 
12-inch  gun  will  give  an  extreme  range  of  something  like  21,000  yards. 
It  is  conceded,  however,  that  accuracy  cannot  be  obtained  at  a  range 
exceeding  say  10,000  to  12,000  yards,  and  this  requires  the  ability  to 
see  the  target,  which  would  be  extremely  difficult  if  modern  seacoast 


68  THE  SERVICE  OF  COAST  ARTILLERY 

batteries  be  the  targets.  On  the  other  hand,  the  maximum  accurate 
effective  range  of  the  land  defenses  is  approximately  12,000  yards,  or 
about  seven  miles,  with  moving  targets  easily  identified. 

It  may  be  stated  that  the  relative  value  of  a  battery  ashore  to  that 
of  one  afloat  is  not  a  matter  of  gun  against  gun;  it  is  a  function  of  the 
relative  degree  of  protection  which  each  enjoys,  as  well  as  the  volume 
of  fire  each  can  deliver.  The  protection  afforded  the  battery  of  a 
seacoast  fortification  is  much  greater  than  that  afforded  the  guns  of 
ships. 

The  protection  of  a  large-caliber  gun  mounted  afloat,  with  its 
mechanism  and  ammunition,  is  limited  to  the  necessities  of  compromise 
as  to  space  and  weight  which  pertain  to  all  marine  construction,  while 
that  of  the  gun  ashore  is  limited  only  by  that  of  cost.  Apart  from  the 
question  of  its  immediate  protection,  the  gun  afloat  is  necessarily 
dependent  upon  its  platform,  that  is,  upon  the  safety  of  the  ship  upon 
which  it  is  mounted,  and  this  is  vulnerable  throughout  its  entire  under- 
water body  to  a  mine  or  submarine  boat,  and,  to  a  lesser  degree,  to  shot 
and  shell.  If  a  ship  is  sunk  the  guns  which  it  carries,  together  with  the 
mobility  which  constitutes  their  special  value,  are  destroyed  and  lost 
to  their  country  for  the  remainder  of  the  war. 

It  is  right  that  a  war  vessel  should  take  this  risk  when  involved  in 
a  contest  against  her  proper  antagonist — the  warships  of  the  enemy— 
but  it  is  indeed  an  exceptional  case  when  a  vessel  should  accept  or 
involve  herself  in  a  contest  with  shore  batteries  and  mine  fields.  The 
cost  even  of  success  in  such  a  contest  would  probably  be  too  great. 
Again,  fortifications  have  a  decided  advantage  in  the  means  afforded 
them  to  determine  the  necessary  data  for  laying  the  guns,  while  owing 
to  the  shortness  of  base  lines  in  the  range-finding  system  afloat,  the 
data  determined  therefrom  must  necessarily  be  less  effective  than  that 
obtained  by  the  longer  base  lines  used  ashore.  It  must  also  be  remem- 
bered that  the  shore  gun,  with  its  emplacement  and  disappearing  car- 
riage, is  completely  protected  from  the  fire  of  the  gun  afloat  and  in  most 
cases  is  entirely  hidden  from  view,  at  the  same  time  having  a  clear 
definition  of  the  target. 

ATTACKS   FROM   THE   SEA 

In  order  that  definite  plans  of  defense  may  be  formulated,  it  is 
necessary  to  assume  that  the  enemy  will  make  one  of  the  several  forms 
of  attack  herein  outlined: 

Frontal    Attack. — If  it  is  assumed  that  the  enemy  will   make  a 


THEORY  AND  PRINCIPLES  OF  COAST  DEFENSE  69 

frontal  attack,  that  is,  will  attempt  after  bombardment,  to  run  by 
the  fortifications,  the  best  means  and  principles  to  follow  would  neces- 
sarily be  to  have  fortifications  strong  enough  to  repel  such  an  attempt 
by  graded  artillery  fire  in  the  outer  defense  zones.  To  conduct  an 
effective  bombardment  the  enemy's  vessels  would  in  all  probability 
steam  successively  to  a  buoy  anchored  at  a  known  distance  from  the 
works,  deliver  their  fire  and  go  out  again. 

It  is  scarcely  probable,  however,  that  a  frontal  attack  would  take 
place  at  any  of  the  more  strongly  fortified  positions.  Nevertheless,  if 
the  armament  at  these  points  compels  the  enemy  to  land  in  order  to 
effect  their  capture,  such  armament  is  fulfilling  its  proper  function  in 
the  role  of  defense. 

This  form  of  attack  would  be  impracticable  until  the  enemy  had 
obtained  command  of  the  sea.  As  long  as  such  command  was  in  doubt, 
it  would  be  his  purpose  to  seek  our  fleet  and  engage  it.  If  unsuccessful, 
it  is  hardly  to  be  expected  that  he  would  attempt  a  frontal  attack 
upon  any  fortification  with  the  intent  of  entering  a  fortified  harbor. 
A  frontal  attack  must,  therefore,  take  up  such  form  more  for  the  purpose 
of  locating  positions  of  the  batteries  than  an  attempt  to  run  by. 

Moreover,  if  a  direct  fr/mtal  attack  of  the  enemy  should  be  successful 
in  silencing  the  fortifications,  neither  the  ships  themselves  nor  their 
personnel  have  the  requisite  tactical  organization  to  complete  the 
victory  by  landing.  They  are  not  able  to  supply  the  necessary  number 
of  men  to  take  actual  physical  possession  of  the  fortified  points  secured, 
capture  the  guns  and  other  property,  guard  the  large  number  of  prisoners 
taken,  and  overcome  the  defense  of  the  coast  artillery  supports,  the 
coast  guard  and  other  available  troops.  It  is  therefore  necessary  that 
the  enemy's  army  be  present  and  ready  to  land  when  the  attack  is 
negotiated,  and  such  a  condition  is  not  likely  to  exist  until  after  com- 
mand of  the  sea  had  been  obtained. 

The  "  Run  By." — The  object  of  a  fleet  in  attempting  to  run  by 
fortifications  would  be  to  enable  it  to  enter  a  harbor  and  operate  in  the 
rear,  as  well  as  to  make  such  a  blow  felt  by  the  destruction  or  capture 
of  the  property  in  such  harbors.  The  matter  of  a  "  run  by  "  has  become 
a  most  difficult  problem  for  a  fleet — and  especially  a  foreign  fleet  oper- 
ating against  the  United  States — since  the  development  of  the  present 
mine  system.  Without  the  mine  fields,  it  is  conceded  as  being  possible 
for  the  fleet  at  full  speed,  at  night  and  under  favorable  conditions  of 
smoke,  fog,  etc.,  to  run  by  the  batteries  without  being  discovered,  or 
without  the  batteries  being  able  to  deliver  an  effective  and  deliberate 
fire.  To  accomplish  this  under  present  conditions,  however,  all  regard 


70  THE  SERVICE  OF  COAST  ARTILLERY 

for  the  mine  fields  must  be  left  out  of  consideration.  They  must  be 
made  ineffective  by  counter  mining — the  success  of  which  is  indeed 
very  doubtful,  if  at  all  effective— or  by  cutting  the  cables  beforehand. 
The  location  of  the  mine  fields  will  always  be  kept  a  secret,  so  the 
matter  of  cable  cutting  must  necessarily  be  done  in  order  to  assure 
success,  although  how  such  an  operation  will  be  successful  is  extremely 
hard  to  outline  when  consideration  is  given  to  the  authorized  floating 
defenses.  The  only  other  means  available  for  the  enemy  would  be  that 
of  dragging  for  cables,  in  which  event  it  would  be  necessary,  for  success, 
to  cover  almost  the  entire  ground  occupied  by  the  mines,  and  it  is 
hardly  possible  that  this  operation  would  be  effective  under  the  condi- 
tions of  security  maintained  by  the  floating  and  shore  defenses,  and 
the  character  of  the  mines  themselves. 

Leaving  out  of  consideration  the  matter  of  fog,  etc.,  the  coast 
batteries  are  practically  as  effective  at  night  with  the  searchlights  in 
action,  as  they  are  in  the  daytime;  and  for  an  enemy  to  effect  a  "run 
by,"  it  must  necessarily  first  put  the  searchlights  out  of  action.  These, 
together  with  the  range-finding  stations,  and  other  fire-control  stations, 
while  apt  to  be  rendered  unserviceable  by  a  chance  shot,  can  only  be 
successfully  destroyed  by  landing  parties. 

It  may  therefore  be  stated  that  a  successful  "  run  by  "  can  only  be 
accomplished  when  the  mine  fields  have  been  put  out  of  action.  The 
days  of  the  "run  by"  fortifications,  like  those  of  charges  by  massed 
bodies  of  infantry,  belong  to  the  warfare  of  the  past  rather  than  to  that 
of  the  future. 

Landings. — During  the  second  period  of  a  war,  or  after  the  navy 
had  been  rendered  ineffective,  the  object  of  a  victorious  enemy  would 
probably  be  to  obtain  final  decision  upon  the  issues  by  invading 
United  States  territory  with  landing  parties,  or  troops  landed  from 
transports,  etc.  There  are  many  points  on  the  coast  at  which  an  army 
might  be  landed,  but  to  make  such  invasion  effective  and  at  all  perma- 
nent, a  suitable  base  must  be  obtained,  that  is,  possession  taken  of  a 
good  harbor  with  terminal  facilities  for  supplies,  etc. 

From  both  military  and  naval  standpoints,  such  a  port  must  be 
captured  or  established  by  the  enemy  before  he  can  make  his  occupation 
effective  and  secure.  It  is  reasonable  to  suppose  he  would  try  to  effect 
a  landing,  and  by  that  means  attempt  to  capture  a  fortified  point,  rather 
than  attempt  it  from  the  water  side,  as  under  the  conditions  of  this 
assumption  it  is  supposed  a  combination  of  armament  and  mines  will 
effectively  prevent  any  modern  navy  from  entering  a  fortified  harbor. 

Bearing  in  mind  historical  cases  of  attacks  on  fortifications,  namely, 


THEORY  AND  PRINCIPLES  OF  COAST  DEFENSE  71 

Sevastopol  and  Port  Arthur,  the  above  assumption  would  seem  reason- 
able, as  both  of  these  fortifications  were  captured  from  the  land  side. 
The  allied  fleets  in  the  first  instance,  and  the  Japanese  in  the  second, 
had  command  of  the  sea,  maintained  a  blockade  and  kept  their  com- 
munications open,  but  left  the  reduction  of  the  strongholds  to  the 
slow  but  certain  process  of  siege  operations.  At  Sevastopol  the  British 
and  French  men-of-war  in  concert  on  one  occasion,  attacked  the  harbor 
forts  ineffectively  and  with  considerable  loss  to  themselves. 

More  recently  at  Port  Arthur,  the  Japanese  vessels  did  not  even 
expose  themselves  to  the  fire  of  the  Russian  land  batteries,  but  waited 
for  their  army  to  reduce  the  fortifications  from  the  land  side. 

The  general  considerations  attending  combat  with  landing  parties, 
belong  to  the  functions  of  the  coast  artillery  supports,  the  coast  guard 
and  the  field  army.  It  is  one  of  the  problems  that  confront  comman- 
ders of  mobile  troops. 

It  is  practically  safe  to  assume  that  the  enemy  would  attempt  to 
effect  a  landing  only  under  one  of  three  conditions. 

The  first  of  these  would  be  when  he  found  a  suitable  unfortified 
place,  uncovered  or  but  sparsely  occupied  by  troops,  and  so  situated 
that  it  would  be  impossible  to  mobilize  an  army  from  the  surrounding 
country  of  such  strength,  and  in  time,  to  defend  or  prevent  the  landing. 
Such  a  point  might  be  found  along  the  coast,  particularly  if  the  plans 
of  the  enemy  were  drawn  with  marked  strategical  insight.  In  other 
words,  with  the  real  idea  of  landing  at  the  north  a  series  of  feints  or 
false  landings,  apparently  in  force,  might  be  demonstrated  at  the  south, 
or  vice  versa. 

At  first  glance  we  might  consider  such  a  line  of  reasoning  as  unsound, 
if  not  altogether  impossible,  under  the  assumption  that  the  force  neces- 
sary to  accomplish  such  an  enterprise  would  prevent  its  execution, 
particularly  in  view  of  the  facilities  for  information  and  transportation 
afforded  us  by  reason  of  our  commercial  telegraphs,  railways,  etc. 
Indeed,  it  would  be  impracticable,  if  we  were  contending  with  a  second- 
class  power  or  one  or  moderate  limits  of  credit  or  men.  However, 
before  Napoleon,  in  the  Marengo  campaign,  emerged  from  the  Great 
St.  Bernard  Pass,  after  the  passage  across  the  Alps,  few  military  special- 
ists could  have  been  found  who  would  have  admitted  the  possibility  or 
likelihood  of  such  an  enterprise.  The  late  Colonel  Wagner,  in  com- 
menting upon  this  feat,  remarks  that  it  would  have  been  impossible  at 
the  present  time  with  the  facilities  now  enjoyed  for  information.  He 
continues,  however,  that  in  all  probability  Napoleon  would  have  won 
with  as  much  ease  to-day  as  he  did  yesterday;  and  the  facts  that 


72  THE  SERVICE  OF  COAST  ARTILLERY 

front  us  are  that  with  all  our  enterprise  and  ingenuity,  our  cables, 
telegraphs,  newspapers  and  fleets,  a  few  years  ago  Cervera's  fleet  came 
over  from  Spain  and  unknown  to  us  sailed  into  the  harbor  of  Santiago 
de  Cuba  without  being  detected  and  without  the  slightest  material 
strategic  attempt  being  made  to  turn  our  heads  to  any  other  point 
than  Cuba. 

The  questions  of  time  and  means  are  undoubtedly  the  leading  things 
to  be  considered.  Landings  in  force  have  the  advantage  of  a  powerful 
covering  base,  namely,  the  protecting  fleet.  Against  this  base  no  force 
of  mobile  troops  would  be  effective.  The  length  of  time  necessary  to 
bring  up  and  land  an  army  with  its  necessary  impedimenta  is  an 
extremely  difficult  problem  to  solve.  The  period,  however,  should  not 
be  in  excess  of  the  time  required  for  the  United  States  to  mobilize  a 
force  strong  enough  to  give  it  combat  of  enough  effectiveness  to  prevent 
its  advance  to  the  nearest  fortified  point,  for  with  the  latter  taken,  the 
fleet — kept  until  that  time  beyond  the  range  of  the  shore  batteries — 
would  sail  quietly  in  and  anchor. 

With  our  navy  destroyed  or  at  points  not  accessible,  and  barring 
storms  that  might  temporarily  dislodge  its  base,  the  danger  from  landings 
in  force  may  be  considered  as  of  grave  import. 

The  second  condition  under  which  landings  could  be  effected  on 
unfortified  portions  of  the  coast,  would  be  after  bombardment  by  the 
fleet.  The  means  of  protection  against  such  fire  is  a  function  of  the 
engineers,  and  a  consideration  to  be  dealt  with  in  the  plans  of  defense 
of  unfortified  portions  of  the  coast.  The  duty  of  the  personnel,  how- 
ever, of  the  mobile  army,  coast  guard,  and  coast  artillery  supports  are 
attached  closely  to  the  means  provided  in  these  plans.  Their  func- 
tions might  be  characterized  as  those  of  a  purely  tactical  nature, 
while  the  plans  themselves  belong  rather  to  the  science  of  strategy. 
In  other  words,  no  plan  of  defense  could  go  to  the  length  of  explaining 
exact  tactical  dispositions.  These  must  of  necessity  be  left  to  the 
professional  abilities  of  the  commanding  officer  on  the  ground.  Hence, 
in  preparing  himself,  his  officers  and  men,  for  the  duty  to  be  performed, 
there  are  set  rules  that  should  be  studied  theoretically  and  developed, 
if  possible  during  peace  time.  It  has  been  said,  with  much  good 
reason,  that  it  is  not  well  to  await  an  ideal  condition  of  affairs  in 
military  instruction,  but  to  make  the  best  of  things  as  they  are,  to 
economize  time  and  utilize  means  as  effectively  as  surrounding 
circumstances  admit. 


THEORY  AND   PRINCIPLES   OF  COAST  DEFENSE  73 


PLAN    OF    LAND    DEFENSE 

Before  drawing  up  the  plan  of  land  defense  for  the  locality  considered, 
it  will  be  necessary  to  make  a  careful  examination  of  the  ground  in  the 
vicinity  with  reference  to  the  following  details: 

(a)  The  best  general  line  to  be  occupied  by  the  infantry. 

(6)  The  best  positions  for  mobile  artillery. 

(c)  The  most  favorable  lines  of  advance  for  the  enemy,  should  he 
succeed  in  effecting  a  landing. 

(d)  The  weak  flank  of  the  position,  and  the  most  favorable  ground 
for  counter  attack. 

(e)  Ground  for  the  reserve,  for  the  general  reserve,  for  mounted 
troops,  and  for  rallying  positions  in  case  of  retreat. 

In  order  to  conceal  the  main  position  as  long  as  possible,  advanced 
lines  may  be  established  in  front  of  the  main  trenches.  Trenches  should 
never  be  constructed  so  as  to  bring  the  troops  against  the  sky  line. 


FIELD    COMBAT 

The  established  rules  of  field  combat,  briefly,  are  as  follows:  An 
engagement  generally  presents  three  distinct  phases,  namely,  the 
preparatory  stage,  the  decisive  action  and  the  completion. 

The  corresponding  distribution  of  troops  should  be  such  as  to  carry 
out  the  following  plan: 

(a)  To  engage  the  enemy,  wherever  he  may  attempt  to  land,  with 
sufficient  troops  to  stop  him. 

(6)  To  withhold  a  part  of  the  available  forces  for  a  powerful  effect 
at  the  decisive  point  or  moment. 

(c)  To  maintain  a  reserve,  screened  from  the  enemy's  view  and 
protected  from  loss,  to  take  part  in  a  vigorous  pursuit  in  case  of  success, 
or  to  avert  complete  disaster  by  disputing  his  advance  in  case  of  failure. 

In  combat  against  landings  in  force  these  phases  would  not  neces- 
sarily be  fully  developed ;  the  preparatory  stage  might  be  brief  and  the 
decisive  attack  begun  suddenly.  Such  combat  is  necessarily  offensive 
and  has  the  advantage  of  the  choice  of  position,  which  should  be  se- 
lected so  as  to  afford  shelter  to  the  defenders  from  bombardment  and  if 
possible  screen  them  from  view.  Ranges  in  the  foreground  should  be 
measured  and  marked. 

The  manner  of  occupying  a  position  will  vary  with  the  nature  of  the 
ground,  and  with  the  strength  and  character  of  the  troops  available. 
It  is  therefore  impracticable  to  apply  fixed  rules. 


74  THE  SERVICE  OF  COAST  ARTILLERY 

The  troops  available  will  generally  be  divided  into  two  principal 
parts — one  for  occupation  of  the  intrenchments,  including  local  reserves ; 
and  the  other  the  general  reserve  for  reinforcing  parts  of  the  line  and 
for  the  delivery  of  the  decisive  counter-attack  or  of  the  offensive  return. 

Should  the  enemy  succeed  in  gaining  a  position  threatening  the  line 
of  defense,  or  penetrate  that  line,  a  counter  attack  becomes  imperative, 
and  the  sooner  it  is  made  the  better,  so  that  the  enemy  may  not  have 
time  to  strengthen  the  ground  he  has  gained.  Such  local  counter- 
attacks are  the  special  duty  of  the  local  reserves;  they  are  made  upon 
the  initiative  of  officers  in  command  of  subdivisions  of  the  defense. 

Should  the  enemy  attempt  an  assault  he  will  be  met  with  rapid  fire 
and  a  counter  charge  with  fixed  bayonets.  Every  available  man  should 
be  brought  up  and  the  enemy  struck  in  flank  if  possible.  If  the  de- 
fenders are  successful  and  the  assailants  abandon  the  offensive  the 
enemy  should  be  pursued  vigorously.  If  retreat  on  the  part  of  the  de- 
fenders is  necessary,  some  artillery  and  intact  infantry  should  occupy 
the  rallying  position  and  the  remainder  of  the  troops  endeavor  to  gain 
the  cover  of  the  rallying  position  and  there  reorganize. 


FIRE    IN   FIELD    COMBAT 

Fire  direction  is  a  function  of  the  company  commanders.  Their 
instructions  as  to  the  general  direction  and  character  of  the  fight  as 
well  as  the  part  their  companies  are  to  take  in  it  are  received  from  the 
next  higher  commanders.  From  the  beginning  of  the  action  collective 
concentrated  controlled  fire  should  be  delivered.  To  each  platoon  and 
section  there  should  be  allotted  a  certain  subdivision  of  the  enemy's 
line  at  which  to  fire,  so  that  the  distribution  may  be  evenly  divided 
along  the  assailant's  front. 

Fire  control,  in  so  far  as  it  pertains  to  seeing  that  the  orders  for  fire 
are  implicitly  obeyed,  that  proper  ranges  are  used,  that  men  are  sup- 
plied with  ammunition,  that  ammunition  is  not  wasted  and  that  the 
fire  is  concentrated  on  the  portion  of  the  enemy's  line  designated,  is  the 
duty  of  the  lieutenants  and  non-commissioned  officers. 


NIGHT   ATTACKS 

The  third  condition  under  which  an  enemy  would  endeavor  to  effect 
a  landing  would  be  either  at  night  or  in  foggy  weather.  In  discussing 
this  condition  the  night  operations  of  the  defense  should  be  considered. 


THEORY  AND  PRINCIPLES   OF  COAST  DEFENSE  75 

On  the  assumption  that  the  enemy  would  attempt  to  land,  outside  of 
the  range  of  the  guns  of  permanent  fortifications,  night  operations  of  the 
defense  should  be  studied  with  a  view  of  rapid  concentration  of  troops 
for  the  decisive  attack.  Nothing  but  the  most  general  rules  for  the 
defensive  can  be  prescribed.  The  outposts  must  exercise  the  utmost 
vigilance,  and  the  dispositions  must  be  such  that  the  line  of  resistance 
can  be  stubbornly  held  and  quickly  reenforced.  Whenever  practicable 
the  position  should  be  covered  with  obstacles,  and  successive  echelons 
placed  in  positions  favorable  for  the  assumption  of  the  offensive. 
Arrangements  should  be  made  to  enable  them  to  form  their  ranks  with 
the  least  possible  delay. 

Smoking,  talking,  laughing  and  other  noises  in  ranks  should  be 
prohibited.  The  watches  of  all  officers  should  be  set  with  those  of  the 
commanding  officer. 

The  infantry  should  withhold  its  fire  as  long  as  possible  and  open 
with  volleys. 

Small  Landing  Parties  differ  from  landings  in  force  in  that  their 
objects  are:  (1)  to  procure  information  as  to  the  position  and  strength 
of  the  land  defense,  condition  of  the  land  front,  the  armament,  and 
morale,  etc. ;  (2)  to  annoy  the  garrison  by  attacks  in  the  nature  of  recon- 
naissance in  force;  (3)  to  attempt  gaining  admission  to  the  fortifica- 
tions by  stealth  or  subterfuge  for  the  purpose  of  destroying  power 
plants,  searchlights,  etc. 

Men  landing  from  boats  under  these  conditions  are  always  at  a 
disadvantage  and  are  especially  subject  to  severe  loss  from  the  fire 
of  the  movable  armament  assigned  to  fortifications,  as  well  as  the  rifle 
fire  of  the  coast  artillery  supports.  Indeed,  such  landing  parties  have 
little  or  no  importance  if  an  efficient  system  of  outposts  and  patrols  is 
constantly  maintained. 


CHAPTER  III 
ORGANIZATION  AND  PERSONNEL 

THE  Regular  Coast  Artillery  troops  are  organized  as  a  corps,  and 
assigned  to  artillery  districts.  The  coast  artillery  reserve  is  composed 
of  regiments,  battalions  and  companies  of  the  organized  militia  perma- 
nently assigned  to  fortifications  at  or  adjacent  to  their  home  stations. 
The  regular  Coast  Artillery  troops  and  the  coast  artillery  reserve  together 
constitute  the  coast  artillery  troops  proper. 

Coast  artillery  supports  are  not  a  part  of  the  Coast  Artillery  troops 
proper.  They  consist  of  mobile  troops  of  the  line  of  the  Army.  When 
assigned  as  such  they  are  under  the  immediate  orders  of  the  Artillery 
District  Commander. 

The  coast  guard  is  not  a  part  of  the  coast  artillery  troops  proper.  It 
consists  of  mobile  troops  of  the  line  of  the  army.  It  is  placed  at 
strategical  points  near  fortified  portions  of  the  coast  line.  It  is  organ- 
ized the  same  as  a  field  army. 

TACTICAL 

For  tactical  purposes  artillery  districts  are  divided  into  Battle 
Commands,  Fire  Commands,  Mine  Commands,  and  Battery  Com- 
mands. The  function  of  each  is  described  in  the  DEFINITIONS. 


ADMINISTRATIVE 

For  purposes  of  drill  and  administrative  organization  the  Regular 
Coast  Artillery  Corps  is  divided  into  companies  and  assigned  to  coast 
artillery  forts  or  posts.  The  strength  of  companies  is  prescribed  in 
regulations.  There  is  no  battalion  or  regimental  organization,  except 
in  the  coast  artillery  reserve,  when  at  their  home  stations,  where  pro- 
visional regimental  or  battalion  organization  is  maintained. 

In  the  regular  service  the  Company,  Post,  District,  Department, 
and  War  Department  constitute  the  administrative  channel. 


ORGANIZATION  AND  PERSONNEL  77 


PERSONNEL 

The  personnel  of  the  Regular  Coast  Artillery  Corps  consists  of  a 
Chief  of  Coast  Artillery,  officers  assigned  to  duty  at  the  War  Depart- 
ment, officers  assigned  to  the  Coast  Artillery  Board,  officers  assigned  to 
the  Coast  Artillery  School,  officers  assigned  to  the  headquarters  of  each 
division  or  department  in  which  coast  artillery  is  located,  and  other 
officers  and  enlisted  men  designated  as  follows: 

District  Commander,  Battle  Commander,  Fire  Commander,  Mine 
Commander,  Battery  Commander,  Range  Officer,  Emplacement  Officer, 
Communication  Officer,  Searchlight  Officer,  Property  Officer,  Mine- 
Field  Officer.  The  duties  of  each  will  be  found  in  the  DEFINITIONS. 

STAFF    OFFICERS 

For  administrative  purposes  coast  artillery  officers  are  assigned  to 
the  following  staff  positions:  At  each  headquarters  of  an  artillery 
district,  an  Artillery  District  Adjutant,  District  Artillery  Engineer, 
Artillery  District  Ordnance  Officer,  and  Artillery  District  Quarter- 
master. 

At  coast  artillery  forts  or  posts  the  corresponding  post  staff  officers 
are  appointed.  The  duties  of  each  will  be  found  in  the  DEFINITIONS. 

COAST   ARTILLERY    RESERVE    OFFICERS 

A  coast  artillery  reserve  officer  assigned  to  any  of  the  commands 
enumerated  above,  when  taking  part  in  drills  or  exercises  at  a  coast 
artillery  fort  or  post,  or  when  mustered  into  the  service  of  the  United 
States,  performs  the  same  duties  so  far  as  compatible  with  those  noted 
for  regular  officers,  unless  otherwise  directed  by  competent  authority. 

If  a  regular  and  a  reserve  officer  of  equal  rank  are  acting  together,  as 
contemplated  in  the  preceding  paragraph,  the  reserve  officer  would  act 
as  assistant  to  the  regular  officer.  In  cases  where  regular  and  reserve 
officers  are  assembled  together  on  duty,  reserve  officers  take  precedence 
next  after  all  regular  officers  of  the  same  rank,  irrespective  of  the 
seniority  of  such  reserve  officers. 

COMMANDS  APPROPRIATE  TO  GRADE 

Colonels  of  coast  artillery  are  usually  assigned  to  staff  duty  at  the 
War  Department,  on  the  Coast  Artillery  Board,  as  commandants  of  the 
Coast  Artillery  School,  and  as  artillery  district  commanders. 


78  THE  SERVICE  OF  COAST  ARTILLERY 

Lieutenant-colonels  as  artillery  district  commanders,  battle,  fire, 
or  mine  commanders,  and  commanders  of  coast  artillery  forts  or  posts. 

Majors  as  battle  commanders,  fire  or  mine  commanders,  and  as 
commanders  of  coast  artillery  forts  or  posts. 

Captains  as  battery  commanders  and  in  command  of  mine,  gun,  or 
mortar  companies.  Also  as  commanders  of  small  coast  artillery  forts 
or  posts. 

Lieutenants  as  communication,  searchlight,  property,  mine-field, 
casemate,  range  or  emplacement  officers;  assigned  to  companies,  or 
staff  duty. 

All  field  and  line  officers  of  coast  artillery  are  subject  to  detail  as 
staff  officers  or  on  special  duty. 

NON-COMMISSIONED    OFFICERS,    ETC. 

In  the  Coast  Artillery  Corps  the  following  non-commissioned  officers 
and  graded  men  are  authorized: 

Sergeant  Major,  Senior  Grade;  Sergeant  Major,  Junior  Grade;  First 
Sergeant;  Quartermaster  Sergeant;  Sergeant;  and  Corporal. 

In  addition  to  the  above  the  following  ratings  are  authorized: 

Master  Electrician;  Engineer;  Electrician  Sergeant,  First  Class; 
Electrician  Sergeant,  Second  Class;  Master  Gunner;  Fireman;  Gunner, 
First  Class;  Gunner,  Second  Class;  Gun  Commander;  Gun  Pointer; 
Plotter;  Observer,  First  Class;  Observer,  Second  Class;  Casemate 
Electrician;  Chief  Planter;  Chief  Loader.  The  duties  of  each  will  be 
found  in  the  DEFINITIONS. 

Other  positions  to  which  the  enlisted  personnel  are  detailed  are  as 
follows:  Mechanic;  Range-Setter;  Meteorological  Observer;  Tide- 
Observer;  Assistant  Plotter;  Range-correction  Computer;  Deflection- 
Computer;  Primary  Arm-Setter;  Secondary  Arm-Setter;  Telauto- 
graph Operator;  Telephone  Operator;  Range  Keeper;  *Reader;  Search- 
light Operator;  Searchlight  Watcher;  Wireless  Operator;  Recorder; 
Orderly;  Musician;  Cook. 

Chiefs  are  assigned  to  the  various  sections,  detachments  and  details 
shown  in  the  drill  regulations. 


CHAPTER  IV 
GUNNERY   AND   BALLISTICS 

IN  this  chapter  it  is  intended  to  make  the  ballistic  formulas  which 
are  necessary  to  the  practical  artilleryman  less  formidable  than  the 
term  implies,  with  the  hope  that  gunners  will  not  instinctively  avoid 
them.  One  need  not  be  an  expert  mathematician  in  order  to  be  a 
practical  gunner  and  successfully  apply  ballistic  formula. 

As  concerns  the  artilleryman,  ballistics  is  divided  into  two  classes: 
First,  that  which  relates  to  the  behavior  of  the  projectile  in  the  gun, 
known  as  "  Interior  Ballistics/'  and  second,  that  which  deals  with  the 
projectile's  action  in  its  flight  through  the  air,  called  "  Exterior  Bal- 
listics." It  is  believed  that  a  comprehensive  understanding  will  be 
had  of  each,  if  the  explanation  is  preceded  by  a  few  words  on  gunnery, 
or  the  art  and  science  of  operating  the  guns  to  which  both  Interior 
and  Exterior  Ballistics  are  to  be  applied. 

GUNNERY 

The  Gun. — A  gun  may  be  called  the  simplest  form  of  gas  engine. 
To  move  the  projectile  through  the  bore  requires  the  expenditure  of 
energy.  The  energy  which  produces  the  force  to  propel  the  projectile 
is  heat,  and  the  heat  carrier  is  gaseous,  hence  the  term  "  gas  engine." 

This  machine  or  gun  is  made  entirely  of  steel;  its  essential  parts 
being  a  tube,  jacket,  breech-bushing,  and  the  A,  B,  C  and  D  rows  of 
hoops.  The  number  of  hoops  has  been  successively  reduced  'and  their 
length  increased,  as  steel  manufacturers  have  become  able  to  make 
larger  forgings;  and  this  increase  in  the  length  of  hoops  has  greatly 
augmented  the  efficiency  of  guns. 

The  tube  is  enveloped  by  a  jacket  and  the  several  rows  of  hoops; 
it  is  inserted  into  the  jacket  from  the  breech  end  and  a  shoulder  upon 
its  exterior  abuts  against  a  corresponding  one  near  the  front  end  of  the 
jacket.  The  outside  diameter  of  the  tube  is  successively  reduced  from 
the  front  end  of  the  jacket,  to  the  muzzle,  by  6  shoulders.  The  jacket 
projects  to  the  rear  of  the  tube  a  sufficient  distance  to  allow  room  for  the 

79 


THE  SERVICE  OF  COAST  ARTILLERY 


screw  box,  or  breech  recess.  Figures 
1,  2  and  3  illustrate  the  method  of 
construction  of  seacoast  cannon. 
The  8-inch  gun,  model  1888  (Fig.  1), 
is  here  used  for  purposes  of  demon- 
stration, by  reason  of  its  being  the 
first  of  the  modern  types  of  built-up 
gun  construction.  In  this  model 
the  jacket  and  C-l  hoop,  the  C-l  and 
C-2  hoops,  and  the  C-2  and  C-3 
hoops,  are  not  directly  locked  to- 
gether. The  remaining  C-hoops,  three 
in  number,  are  locked  together  with 
a  lip  on  the  forward  hoop  by  over- 
lapping a  lip  on  the  rear  one,  the 
contact  surface  of  the  rear  one  being 
a  frustum  of  a  cone,  with  the  smaller 
base  at  the  breech  end. 

In  front  of  the  C-5  hoop  is  a  key 
ring,  which  being  part  in  a  groove 
of  the  tube  and  part  in  front  of  the 
hoop,  prevents  forward  motion  of 
any  of  the  C-hoops  in  the  rear.  The 
C-6  hoop  is  fastened  to  the  tube  by 
three  radial  securing  pins.  Overlap- 
ping the  front  end  of  the  jacket  and 
covering  the  C-l,  C-2  and  part  of 
the  C-3  hoops,  there  are  three 
D-hoops,  locked  together  by  lips 
similar  to  those  on  the  C-hoops  and 
having  three  radial  securing  pins 
passing  into  the  D-3  and  the  C-3 
hoops.  Five  A-hoops,  the  second  of 
wThich  is  the  trunnion  hoop,  cover 
the  jacket  and  part  of  the  D-l  hoop. 

The  trunnion  hoop  has  the  shock 
of  discharge  transmitted  to  it 
through  a  shoulder  on  the  jacket. 
Into  the  portion  of  the  jacket  pro- 
jecting beyond  the  breech  and  the 
tube  is  screwed  the  steel  breech 


GUNNERY  AND  BALLISTICS 


81 


bushing,  which  on  its  interior  is  threaded  to  receive  the  breechblock. 
The  breech  bushing  is  secured  against  unscrewing  by  four  spline  screws, 
halved  into  it  and  the  jacket.  A  space  of  0.05  inch  is  left  between  the 
breech  of  the  tube  and  the  breech  bushing.  At  the  interior  of  this 


HoopsArow 

j  / Hoops  B  row 


"\\  Ijffify 

\  x1^'"^1 


/?'       24*       36"      48° 


FIG.  2. 

• 

joint  there  is  a  copper  ring,  given  a  compression  of  0.01  inch  between 
the  tube  and  bushing. 

The  trunnion  band  is  also  a  hoop,  by  which  connection  is  made  with 
the  carriage  of  the  piece.  The  trunnions  are  the  cylindrical  arms 
supporting  the  piece  when  mounted. 


j  r-Breech  Bushing. 
^Copoer  Ricking 
__[  r~^  »•?•  -^ 

55^ 


>/>"^-/?V^V/      >PJ 

^L 


a/y     je' 


!  Jacket!  ^Gas Check 5eal:\  \/fc^/%'-Trunnion Hoop. 

Centering  Slope-  -' 
k /4/./2S' 


FIG.  3. 


The  rim  bases  are  the  shoulders  uniting  the  trunnions  with  the 
trunnion  band.  The  face  of  the  trunnion  and  the  face  of  the  rim  bases 
are  their  end  surfaces.  The  section  of  the  gun  between  the  rear  of  the 
trunnion  band  and  the  breechplate  is  called  the  breech  reinforce,  while 


82  THE  SERVICE  OF  COAST  ARTILLERY 

the  section  between  the  front  of  the  trunnion  band  and  the  front  of  the 
muzzle  is  called  the  chase. 

The  bore  is  the  hollow  portion  in  the  center  of  the  piece,  and  is 
subdivided  into  the  following  parts,  commencing  at  the  breech  end 
of  the  tube:  Gas  check  seat  (conical),  powder  chamber  (cylindrical), 
centering  slope,  forcing  cone,  shot  chamber  and  the  main  bore.  The 
centering  slope  is  used  for  the  purpose  of  bringing  the  axis  of  the  pro- 
jectile to  coincide  with  the  axis  of  the  bore,  the  copper  rotating  band 
on  the  projectile  also  stopping  it  at  its  proper  distance  forward,  by 
seating  it  in  the  slope.  At  the  junction  of  this  slope  and  the  forcing 
cone  the  rifling  commences,  beginning  flat  and  gradually  increasing 
to  its  proper  height  and  gauge.  The  tube  is  closed  at  the  breech  end 
of  the  gun  by  the  breechblock. 


THE    BREECH   MECHANISM 

The  breech  mechanism  of  the  gun  considered  consists  of  the  breech- 
block, obturator,'  breechplate,  rotating  crank,  tray  latch,  securing 
latch  and  hinge  pin. 

In  studying  the  breech  mechanism,  probably  the  best  method  is  to 
dismantle  it.  The  illustration  shown  in  Fig.  4  gives  an  excellent  idea 
of  the  location  of  parts  herein  described,  as  well  as  an  illustrated  nomen- 
clature of  this  model  of  breech.  The  principal  parts  of  the  breech- 
blocks are  3  threaded  sectors,  3  slotted  sectors,  2  guide  grooves,  vent 
cover  and  translating  stud.  The  block  is  threaded  with  a  V  thread 
with  rounded  top;  the  rear  portion  is  left  unthreaded  to  prevent  the 
entrance  of  dust.  The  threaded  portion  is  divided  into  6  equal  seg- 
ments, 3  threaded  and  3  slotted.  The  2  guide  grooves  are  cut  in  the 
bottom  slotted  sector  30  degrees  each  side  of  the  element  of  the  unlocked 
block ;  they  fit  upon,  and  pass  over  the  rails  of  the  console  or  tray  when 
the  block  is  drawn  to  the  rear.  In  the  model  considered,  two  handles 
are  cut  out  of  the  solid  metal  upon  the  rear  end  of  the  block,  for  use  in 
case  of  failure  of  the  mechanism. 

The  vent  cover  is  a  steel  arm,  mounted  in  a  mortise  in  the  block, 
and  suspended  on  the  vent-cover  screw.  By  means  of  a  shoulder  in  the 
bronze  bushing,  which  is  stationary  in  the  breechplate,  the  vent  cover 
is  constrained  to  move  when  the  block  is  rotated,  so  as  to  cover  the  vent, 
over  which  it  remains  until  the  block  is  returned  to  is  locked  position. 
The  translating  stud,  attached  to  the  rear  face  of  the  block,  by  a  screw 
in  a  slotted  seat,  projects  radially  from  the  face  of  the  block.  When 


GUNNERY  AND  BALLISTICS 


83 


84  THE  SERVICE  OF  COAST  ARTILLERY 

the  latter  is  rotated  the  60  degrees  necessary  to  unlock  it  the  stud 
revolves  into  the  groove  in  the  translating  roller. 

The  obturator  consists  of  the  mushroom  head  and  stem,  gas-check 
pad,  front  and  rear  exterior  split  rings,  filling-in  disk,  obturator-spindle 
nut,  locking-nut  and  the  obturator-spindle  washers.  The  vent  is 
drilled  through  the  spindle  in  front  of  which  there  is  a  copper  bushing- 
plug  forced  into  an  undercut  on  the  face  of  the  mushroom  head;  in 
passing  through  this  plug,  the  vent  contracts  from  0.2  to  0.1  inch,  or 
one-tenth  of  an  inch.  This  bushing  may  be  replaced  when  badly 
eroded.  The  rear  end  of  the  vent  channel  (old  model)  is  elongated 
and  threaded  for  an  obturating  primer,  used  to  ignite  the  charge. 

The  gas-check  pad  is  made  of  asbestos  and  tallow,  inclosed  in  a 
canvas  cover. 

The  exterior  split  rings  are  of  steel,  split  diagonally  through  one 
side.  They  are  slightly  larger  than  the  conical  seat  and  are  sprung 
together  in  being  forced  into  place. 

The  interior  ring  is  of  similar  construction  but  slightly  smaller  than 
the  spindle.  The  filling-in  disk  acts  as  a  washer  in  the  rear  of  the  pad, 
a  shoulder  on  its  front  face  supports  the  interior  edge  of  the  rear  split- 
ring,  and  a  fillet  on  the  rear  face  of  the  mushroom-head  performs  the 
same  office  for  the  front  split-ring. 

The  obturator-spindle  nut  is  screwed  on  the  rear  end  of  the  stem 
with  a  right-hand  thread;  it  draws  the  obturator  head  and  gas  check 
to  a  bearing  against  the  face  of  the  block;  it  abuts  against  the  spindle 
washers,  and  has  under  its  front  edge  a  thin  steel  spring  washer  designed 
to  keep  out  dust.  In  rear  of  the  spindle  nut  is  a  locking  nut,  screwed 
on  with  a  left-hand  thread,  designed  to  prevent  the  spindle  from 
unscrewing. 

The  four  obturator-spindle  washers  are  alternately  bronze  and 
steel.  The  object  of  having  one  of  bronze  and  one  of  steel  is  to  reduce 
friction,  taking  advantage  of  the  principle  that  metals  of  different 
kinds,  bearing  upon  each  other,  have  less  friction  than  those  of  the  same 
kind.  They  are  assambled  with  a  bronze  washer  in  front,  and  the  others 
alternately  steel  and  bronze. 

The  breechplate  is  a  steel  casting  attached  to  the  breechface  by 
12  large  screw  bolts.  Its  function  is  to  cover  the  rotating  gears  and 
connect  the  tray  with  the  gun  by  means  of  the  hinge  pin.  On  it  are 
mounted  the  rotating  gears  and  their  journals,  the  gear  segment  actuated 
by  them,  the  bronze  bushing  seat  of  the  gear  segments,  and  the  securing 
latch.  On  its  rear  face  are  the  hinge-pin  ears,  and  the  rear-sight  seat. 
The  recess  in  its  face  acts  as  a  catch  for  the  tray  latch. 


GUNNERY  AND  BALLISTICS  85 

The  bronze  bushing  for  the  gear  segment  is  permanently  attached 
to  the  plate  by  4  screw  bolts  in  a  recess  in  its  front  face.  It  supports 
the  gear  segment  in  rear  and  on  its  outer  surface  and  is  provided  with 
oil  channels  in  its  face,  to  facilitate  lubrication. 

The  rotating  crank  and  gears  are  the  means  of  unlocking  the  block. 
They  consist  of  the  gear  segment,  rotating  pinion,  the  rotating  crank 
and  associate  parts.  The  steel  gear  ring  encircles  the  breechblock  and 
is  mounted  in  the  bronze  bushing;  from  this  ring  projects  radially  the 
gear  segment  of  70  degrees,  in  which  gear  teeth  are  cut. 

The  gear  ring  fits  over  the  cylindrical  portion  of  the  block  with  a  lug 
extending  inward  into  the  upper  right-hand  slotted  sector  prolonged 
to  the  rear  to  receive  it.  It  acts  as  a  key  in  this  slot  to  cause  the  block 
to  rotate.  When  the  latter  is  withdrawn  from  the  screw  box,  the 
slotted  sector  slides  from  under  the  lug. 

The  pinion  is  a  small  gear  whose  function  is  to  rotate  the  gear 
segment  into  which  it  meshes.  Its  journal,  mounted  in  a  bronze  sleeve 
seated  in  the  upper  part  of  the  breechplate,  extends  to  the  rear  beyond 
the  face  of  the  breechplate,  and  has  the  rotating  crank  mounted  upon 
its  square  end,  secured  by  a  nut  and  stay  pin.  By  it  the  pinion  is 
turned,  which  rotates  the  gear  segment,  and  in  turn,  the  block.  Over 
the  two  faces  of  the  pinion  there  are  oil  holes,  closed  by  screws,  for  the 
lubrication  of  the  rotating  gears. 

There  is  a  spring  catch  mounted  in  the  face  of  the  crank  arm,  by 
which  the  gear  system  is  locked  when  the  breech  is  closed  and  the  block 
rotated  to  its  firing  position.  This  catch  consists  of  a  bolt,  a  spiral 
spring,  a  housing  nut  and  a  winged  nut.  The  bolt  is  seated  with  its 
head  projecting  to  the  front,  through  the  crank  arm.  Its  forward  end 
is  beveled  on  one  side,  and  squared  on  the  other.  It  is  held  in  bearing 
against  its  seat  by  a  spiral  spring  on  its  back,  compressed  by  the  housing 
nut  screwed  over  it.  The  rear  end  of  the  bolt  is  threaded  and  has  a 
winged  nut  mounted  upon  it,  having  the  projecting  lug  on  one  side. 
When  the  nut  is  revolved  ISO  degrees,  so  that  the  bolt  presents  its 
beveled  side  in  the  direction  of  rotation,  the  crank  may  be  revolved, 
carrying  the  gear  segment  to  either  of  its  extreme  positions.  The 
handle  of  the  rotating  crank  is  covered  with  a  loose  sleeve  to  facilitate 
turning. 

By  the  rotation  of  the  block,  the  translating  stud  on  the  block  is 
revolved  into  the  thread  of  the  translating  roller,  and  the  block  is  in 
position  to  be  drawn  directly  to  the  rear  of  the  breech  recess  onto  the 
tray. 

The  tray  or  console  is  of  bronze,  mounted  in  the  rear  of  the  breech 


B6  THE  SERVICE  OF  COAST  ARTILLERY 

and  supported  by  a  hinge  pin  on  the  right-hand  side,  the  ears  being 
cast  in  the  breechplate.  The  parts  are  the  tray  proper,  the  translating 
roller  and  crank,  the  tray  latch,  and  the  catch  for  the  securing  latch. 

The  translating  roller  is  seated  in  a  right-hand  thread  in  the  upper 
surface  of  the  body  of  the  tray;  it  has  two  independent  threads  cut  in 
opposite  directions  on  its  surface.  The  translating  stud  engages  in  the 
left-hand  thread  in  the  roller. 

The  translating  crank  is  mounted  on  the  squared  end  of  the  roller. 
The  rotation  of  this  crank  causes  the  roller  to  screw  in  its  right-hand 
thread,  and  hence,  travel  back  in  the  tray,  drawing  the  block  with  it. 
It  also  causes  the  translating  stud,  attached  to  the  block,  to  travel 
as  a  nut  in  the  left-hand  thread.  Thus  a  double  motion  of  translation 
is  given  to  the  block,  drawing  it  onto  the  tray  by  fewer  revolutions  of 
the  crank  than  if  either  of  the  threads  acted  upon  it  singly.  In  the 
reverse  motion,  the  tray  latch  serves  to  secure  the  tray  to  the  face  of  the 
breech,  while  the  block  is  translated  into  its  seat  in  the  screw  box. 

The  tray  latch  is  mounted  in  a  longitudinal  slot  in  the  web  on  the 
under  side  of  the  tray,  on  a  latch  bolt.  Its  front  end  terminates  in  a 
hook  lip  which  engages  in  a  catch  seat  recessed  in  the  breechplate. 
On  its  rear  end  is  a  transverse  handle.  A  spring  bolt  mounted  in  the 
tray,  above  the  latch,  holds  it  so  that  it  cannot  be  unlatched  while 
its  bolt  is  covered  by  the  translating  roller.  When  the  latter  is 
quickly  withdrawn  beyond  it,  the  relation  between  the  excess  of  weight 
in  front  of  the  latch  journal  and  the  tension  of  the  bolt  spring  is  such 
that  the  jar  will  unlatch  it.  The  tray  may  then  be  swung  about  its 
hinge  pin  until  caught  by  the  securing  latch,  thus  uncovering  the  screw 
box.  The  securing  latch  is  mounted  in  a  recess  in  the  breechplate, 
through  which  its  handle  protrudes  on  the  left,  and  its  catch  end  on  the 
right.  Its  pivot  is  a  screw  bolt  passing  through  the  lower  hinge  ear, 
hinge  pin  and  breechplate.  Its  latch  lip  engages  in  a  catch  on  the  diag- 
onal web  of  the  tray.  It  may  be  released  by  lifting  the  handle,  or 
pressing  down  the  latch  end. 

The  hinge  pin  is  a  cylindrical  bar  mounted  in  two  ears  on  the  side 
of  the  breechplate;  it  is  lubricated  from  an  oil  hole  in  the  upper  hinge 
ear.  It  is  entered  from  below  and  held  in  position  by  the  same  screw 
bolt  upon  which  the  securing  latch  is  pivoted. 

The  type  of  gun  construction  described  in  this  chapter  is  known  as 
the  "  built-up  "  cannon,  designed  to  utilize,  to  the  best  advantage, 
the  elastic  qualities  of  the  metal.  No  portion  of  the  bore  of  a  gun 
should  be  strained,  either  at  rest  or  during  firing,  beyond  its  elastic 
limit. 


GUNNERY  AND   BALLISTICS  87 

The  elastic  limit  of  a  metal  is  that  point  beyond  which,  if  it  is 
strained  either  by  extension  or  compression,  a  permanent  set  will  take 
place.  There  is  an  elastic  limit  of  compression,  as  well  as  extension, 
and  if  the  metal  is  strained  beyond  either  limit,  permanent  deformation 
will  occur.  If  the  strain  is  continued,  a  rupture  will  take  place  when 
the  ultimate  strain  is  exceeded.  In  a  gun  made  of  a  single  piece  of 
homogeneous  steel  in  its  natural  condition,  with  no  initial  compression 
or  extension,  the  metal  at  the  bore  cannot  be  stretched  by  the  expansion 
of  the  powder  gases  beyond  the  limit  of  elasticity  for  extension  without 
a  permanent  "  set'"  taking  place.  If,  however,  the  gun  of  the  same 
exterior  dimensions  be  made  of  concentric  tubes,  properly  assembled, 
so  that  the  metal  at  the  surface  of  the  bore  is  contracted  to  its  elastic 
limit  for  compression,  this  surface  will,  in  firing,  stand  a  corresponding 
stress  necessary  to  stretch  it  back  to  the  normal  condition  of  the  first 
cannon,  and,  therefore,  it  may  be  further  strained  so  as  to  utilize  the 
elastic  qualities  for  extension.  As  the  greatest  strain  is  at  the  bore, 
this  portion  of  the  wall  is  compressed,  when  at  rest,  up  to  its  elastic 
limit  for  compression,  and  it  is  extended,  when  under  the  stress  of  the 
powder  gases,  nearly  or  quite  up  to  its  elastic  limit  for  extension. 
It  is  to  obtain  this  greater  tangential  strength  that  modern  cannon  are 
built  up  in  the  manner  just  described.  The  tangential  strength  of  a 
cannon  is  the  resistance  it  offers  to  being  torn  apart  in  a  plane  parallel 
to  its  axis. 

RIFLING   AND    ITS    TWIST 

In  order  to  give  elongated  projectiles  angular  velocity  of  rotation, 
and  thereby  cause  them  to  rotate  around  their  longer  axis,  spiral 
grooves  are  cut  in  the  bore  of  seacoast  cannon.  Attached  to  the  base 
of  projectiles  is  a  soft  copper  band,  which  is  forced  into  the  grooves 
when  the  gun  is  fired.  This  band  being  rigidly  attached  to  the  pro- 
jectile, the  motion  of  rotation  is  transmitted  to  the  projectile,  and  it 
turns  around  its  longer  axis  as  it  moves  through  the  bore.  This  rota- 
tion of  the  projectile  around  its  longer  axis  gives  greater  accuracy  of 
flight,  by  keeping  the  projectile  tangent  to  the  trajectory,  thereby 
presenting  the  surface  of  least  resistance  to  the  air  and  thus  giving 
greater  range  and  penetrative  power. 

As  stated  in  the '  DEFINITIONS,  grooves  are  the  spiral  cuts  made  in 
the  bore,  and  lands  the  spaces  between  two  adjacent  grooves. 

Although  a  great  factor  in  the  accuracy  of  fire,  rifling  is  also  the 
source  of  weakness  in  guns,  due  to  the  erosive  effect  of  the  powder 


88  THE  SERVICE  OF  COAST  ARTILLERY 

gases  on  the  bore  at  the  junction  of  the  lands  and  the  grooves.  Since 
first  introduced  into  gun  construction,  the  tendency  has  been  to  reduce 
the  depth,  and  increase  the  number  of  grooves.  In  the  United  States 
coast  artillery  service,  the  number  of  grooves  is  usually  6  times  the 
caliber,  their  width  approximately  thirty-seven  one-hundredths  of  an 
inch,  and  their  depth  from  six  to  seven  one-hundredths  of  an  inch. 

The  rifling  commences  at  the  junction  of  the  centering  slope  with 
the  forcing  cone.  The  tops  of  the  lands,  at  this  point,  are  cut  down  so 
that  less  power  is  required  at  first  to  force  them  through  the  copper 
rotating  band  on  the  projectile.  The  twist  of  rifling,  i.  e.,  the  inclina- 
tion of  the  grooves  to  the  axis  of  the  bore  at  any  point,  increases  from 
1  turn  in  50  calibers  at  its  origin,  to  1  turn  in  25  calibers  at  a  point 
several  inches  in  rear  of  the  muzzle,  and  retains  this  latter  twist  uni- 
formly up  to  the  muzzle.  In  other  words,  the  projectile,  at  the  start, 
would  make  one  complete  revolution  around  its  longer  axis  in  passing 
over  a  distance  of  400  inches  for  an  8-inch  rifle,  500  inches  for  a  10-inch 
rifle  and  600  inches  for  a  12-inch  rifle;  its  velocity  of  rotation  gradually 
increasing  as  it  passes  through  the  bore  until  at  a  point  near  the  muzzle 
its  velocity  is  such  that  it  would  make  one  complete  revolution  in  passing 
over  a  distance  of  200  inches  for  an  8-inch  rifle,  250  inches  for  a  10-inch 
rifle  and  300  inches  for  a  12-inch  rifle,  or  the  projectile  is  turning  twice 
as  fast  as  at  the  start.  The  twist  is  then  uniform  to  the  muzzle  in  order 
to  steady  the  projectile  as  it  leaves  the  gun. 

When  the  inclination  of  the  grooves  is  constant,  the  twist  is  said  to 
be  uniform.  When  it  increases  gradually  from  the  breech  towards  the 
muzzle,  the  twist  is  said  to  be  increasing.  In  the  United  States  service, 
the  rifling  of  seacoast  guns  and  mortars  is  increasing — for  the  guns — 
from  1  turn  in  50  calibers  at  the  breech,  to  1  turn  in  25  calibers 
at  a  distance  of  about  2  calibers  from  the  muzzle,  from  which  point 
to  the  muzzle  it  is  uniform;  for  mortars,  from  1  turn  in  40  or  42 
calibers,  to  1  turn  in  20  or  25  calibers. 

With  rapid-fire  guns,  the  twist  is  different  in  most  cases.  In  the 
6-pounder  (Driggs-Seabury  and  Driggs-Schroeder)  the  twist  is  from 
0  to  1  in  26  calibers.  In  the  4-inch  (Driggs-Schroeder),  and  the  6-inch 
rifle,  model  of  1905,  it  is  practically  the  same.  The  twist  in  the 
4.72-inch  Armstrong,  40  caliber,  is  from  1  in  100  to  1  in  34  calibers, 
and  the  same  gun,  50  calibers  long,  has  a  twist  of  rifling  from  1  in 
600  to  1  in  30  calibers. 

The  necessity  for  the  increasing  twist  of  rifling  will  be  readily  under- 
stood when  it  is  considered  that  as  the  projectile  starts  from  its  seat, 
on  the  first  part  of  its  travel  through  the  bore,  the  pressure  of  the 


GUNNERY  AND  BALLISTICS  89 

powder  gases  rise  to  a  maximum,  and  the  angular  velocity  is  impressed 
upon  the  projectile  at  this  point  also.  It  is  necessary,  therefore,  that 
the  least  resistance  to  starting  be  offered  by  the  projectile  at  this  point. 
With  an  increasing  twist,  the  projectile  takes  the  grooves  gradually, 
and  the  strain  on  the  gun  is  not  very  great.  With  uniform  rifling,  the 
gun  would  be  submitted  to  the  greatest  pressure  due  to  the  starting, 
and  at  the  same  time  would  be  subjected  to  the  greatest  pressure  due 
to  the  rotation  of  the  projectile,  which  would  unnecessarily  strain  the 
gun.  As  the  projectile  moves  along  the  bore,  the  pressure  of  the  powder 
gases  falls  off  while  the  twist  is  gradually  increasing  until  it  reaches 
the  final  value  necessary  to  impart  the  desired  angular  velocity  to  the 
projectile.  The  pressures  are  thus  more  uniformly  distributed  along 
the  bore  and  the  gun  strained  less  at  the  start,  while  the  final  velocity 
of  rotation  is  as  great  is  if  the  rifling  had  been  uniform. 

THE    PROJECTILE    IN    THE    GUN 

Explosion,  the  principle  of  propulsion  employed  in  modern  artillery, 
is  simply  the  expansion  of  gases  released  by  the  decomposition  of 
chemical  substances.  The  gases  thus  liberated  exert  an  equal  pressure 
at  all  points  on  the  surfaces  which  they  touch.  The  propulsive  energy 
of  these  forces  is  controlled  and  regulated  by  the  mechanism  of  the  gun, 
and  absolute  precision  in  their  use  is  the  first  condition  both  of  safety 
and  efficiency. 

The  potential  energy  stored  up  in  a  pound  of  powder,  when  expand- 
ing to  infinity,  is  capable  of  doing  576  foot-tons  of  work.  In  the  bore 
of  the  gun  the  space  in  which  gases  are  free  to  expand  is  limited,  and 
the  gases  from  a  pound  of  powder  expanding  to  the  volume  of  the  bore 
do  approximately  only  75  foot-tons  of  work.  This  therefore  is  the  usual 
energy  available  to  do  the  total  work  in  the  gun.  The  other  501  foot- 
tons  of  energy  cannot  be  utilized  because  of  the  limited  length  and 
diameter  of  the  bore.  Again,  a  considerable  portion  of  the  total  work 
in  the  gun  is  lost  in  heating  the  gun;  expanding  the  walls  of  the  gun; 
driving  the  column  of  air  in  front  of  the  projectile  out;  driving  out  the 
products  of  combustion,  deforming  the  rotating  band;  overcoming  the 
friction  in  the  bore;  giving  rotation  to  the  projectile,  and  finally, 
accelerating  the  projectile,  that  is,  gradually  increasing  its  velocity 
from  rest  until  it  attains  its  final  initial  velocity  at  the  muzzle  with 
which  the  projectile  starts  in  its  path  through  the  air. 

As  the  principal  object  is  to  give  acceleration  to  the  projectile  it  is 
important  to  know  how  much  of  the  total  work  in  the  gun  can  be 


90  THE  SERVICE  OF  COAST  ARTILLERY 

Utilized  for  this  purpose.  The  ratio  of  the  useful  work  to  the  total 
energy  of  the  powder  is  called  the  "  coefficient  of  useful  effect/'  or  the 
"  coefficient  of  efficiency,"  and  has  been  shown  by  experiment  to  be 
between  80  and  90  per  cent,  of  the  total  work  in  the  gun.  If  a  charge 
of  powder  is  burned  in  a  rigid  space,  that  is,  one  that  has  a  fixed  capacity, 
the  expansive  force  of  the  gas  will  at  any  instant  depend  upon  the 
amount  of  gas  that  has  been  formed  and  its  mean  temperature.  As  the 
amount  of  gas  and  its  temperature  increase  the  expansive  force  will 
increase.  If  at  any  instant  the  space  in  which  the  powder  is  burning 
be  increased,  the  other  conditions  remaining  the  same,  the  expansive 
force  will  decrease.  In  a  gun,  the  space  in  which  the  powder  is  burning 
has  a  fixed  capacity  until  the  projectile  starts  to  move,  after  which  the 
space  increases.  The  pressure  on  the  walls  of  the  gun  and  on  the  base 
of  the  projectile  at  any  instant  depends  upon  the  expansive  force  of 
the  gas  at  that  instant,  as  well  as  the  increase  of  expansive  force  due 
to  an  increase  of  the  amount  of  powder  burned,  or  to  temperature. 
If  this  is  greater  than  the  decrease  of  expansive  force  due  to  increase 
in  the  space  it  occupies,  the  pressure  on  the  walls  of  the  gun  and  on  the 
base  of  the  projectile  is  increasing.  When  the  decrease,  due  to  the 
increase  in  the  space,  is  greater  than  the  increase  due  to  the  amount 
of  powder  burned,  or  to  temperature,  the  pressure  falls  off. 

Theoretically,  the  last  atom  of  powder  should  be  converted  into  gas 
as  the  projectile  leaves  the  bore.  The  more  gradually  the  projectile  is 
evolved,  the  less  the  strain  on  the  gun;  but  the  greater  must  be  the 
length  of  the  bore  in  order  that  all  the  power-charge  may  be  converted 
into  gas  before  the  projectile  leaves  the  bore. 

What  happens  in  a  gun  is  this:  The  explosion  of  the  powder-charge 
gives  rise  to  a  large  amount  of  gas,  which  expands,  and  the  pressure 
from  the  same  acting  on  the  base  of  the  projectile  starts  the  projectile 
to  move  in  the  bore  of  the  gun.  The  pressure  increases  up  to  a  certain 
amount  and  as  the  space  in  which  the  powder  charge  is  burning  is 
increasing  as  the  projectile  moves  through  the  bore,  the  pressure  com- 
mences to  fall  off.  The  greatest  pressure  acting  on  the  base  of  the 
projectile  is  called  the  maximum  pressure,  and  this  is  the  pressure 
indicated  by  the  crusher  gauge.  For  any  gun,  the  maximum  pressure 
must  not  be  exceeded. 

The  form  and  size  of  the  powder  grain  should  be  so  regulated  as  to 
produce  the  greatest  possible  initial  velocity  with  a  maximum  pressure 
not  exceeding  that  which  is  allowed  for  the  gun.  It  is  sufficient  to  say 
that  within  certain  limits,  the  larger  the  grain,  the  less  will  be  the 
initial  burning  surface  per  pound  of  powder,  and  the  less  will  be  the 


GUNNERY  AND  BALLISTICS  91 

maximum  amount  of  pressure  produced  for  a  given  charge  of  powder. 
Due  to  this  fact,  the  larger  the  grain,  the  larger  the  charge  of  powder 
that  can  be  used,  as  a  rule,  and  therefore  a  greater  muzzle  velocity. 
As  the  size  of  the  grain  is  increased  the  percentage  of  the  grain  which 
will  be  consumed  while  the  projectile  is  in  the  bore  is  decreased,  leaving 
a  certain  portion  of  each  grain  unburned  when  the  projectile  leaves 
the  muzzle.  For  this  reason,  the  size  of  the  powder  grain  can  be  in- 
creased within  certain  limits  only.  When  the  point  is  reached  at  which 
the  weight  of  the  unburned  powder  will  equal  the  additional  amount 
of  powder  which  has  been  put  in  the  chamber,  no  further  increase  of 
velocity  can  be  obtained.  If  we  continue  to  increase  the  size  of  the 
grain  without  increasing  the  charge  the  velocity  will  fall  off. 

For  each  class  of  gun,  therefore,  there  is  a  limit  to  the  size  of  grain, 
which  must  not  be  exceeded.  There  is  also  a  limit  in  the  opposite 
direction  and  it  is  possible  to  produce  dangerous  pressures  in  a  gun  by 
using  a  small  charge  of  powder  where  the  grain  is  too  small  for  the  gun 
in  question.  For  this  reason,  powder  should  not  be  used  in  a  gun  for 
which  it  is  not  designed,  or  it  should  be  used  in  a  gun  of  smaller  caliber 
than  that  for  which  it  is  designed,  and  never  for  one  of  larger  caliber. 
The  rate  at  which  gas  is  emitted  from  a  burning  grain  is  dependent 
upon  its  rate  of  burning,  and  the  area  of  the  burning  surface. 

The  ratio  of  burning  increases  with  the  pressure  and  also  with  the 
temperature  of  the  inflamed  gases.  The  larger  the  grain,  the  less  will 
be  the  area  of  burning  surface,  per  pound  of  powder,  and  the  slower 
will  be  the  rate  of  emission  of  gas  for  the  same  rate  of  burning.  For 
every  grain  of  powder,  no  matter  what  form,  there  is  always  one  dimen- 
sion, which,  when  burned  through,  the  entire  grain  is  consumed.  This 
dimension  is  known  as  the  "  least  dimension,"  and  is  sometimes  called 
the  "  critical  dimension "  of  the  grain.  In  the  multi-perforated 
grain, — the  kind  used  with  modern  seacoast  guns, — or  with  smokeless 
powder,  the  critical  dimension  is  the  thickness  of  the  web  between  the 
perforations.  For  example :  If  two  tubular  grains  are  the  same  length, 
one  of  them  one-half  inch  in  diameter  and  the  -other  one  inch  in  diameter, 
both  having  the  same  thickness  of  wall  (one  eighth-inch)  it  is  manifest 
that  as  soon  as  the  wall  is  burned  through  both  grains  will  have  been 
consumed.  The  grain  which  is  one  inch  in  diameter  would  weigh  about 
twice  as  much  as  the  other,  and  twice  the  amount  of  gas  would  be  evolved. 
For  similar  guns,  the  critical  dimension  of  the  grain  should  be  in  pro- 
portion to  the  caliber  of  the  gun. 

When  a  grain  is  said  to  be  too  large  or  too  small  for  a  gun,  too 
quick  or  too  slow  for  a  gun,  it  is  the  critical  dimension  that  is  referred 


92  THE  SERVICE  OF  COAST  ARTILLERY 

to.  The  denser  the  powder,  the  slower  will  be  the  combustion.  An 
extremely  hard  and  very  smooth  grain  is  difficult  to  ignite.  Uniformity 
of  action  of  powder  is  dependent  upon  the  ignition  and  inflammation  of 
the  charge.  By  ignition  is  meant  setting  fire  to  the  charge,  and  by 
inflammation  is  meant  the  spread  of  the  fire  from  grain  to  grain  over  the 
surface  and  into  the  perforations  of  the  several  grains.  It  is  desirable 
to  produce  as  nearly  as  possible  a  simultaneous  ignition  of  the  entire 
charge  in  order  to  eliminate  the  variation  in  the  rate  of  emission  of 
gas,  due  to  an  irregular  spread  of  inflammation  from  grain  to  grain.  A 
charge  composed  of  large  grains  inflames  quicker  than  one  composed 
of  small  grains;  this  is  due  to  the  larger  opening  between  the  grains. 
A  grain  with  large  or  multi-perforations  inflames  more  readily  than  one 
with  small  perforations.  The  longer  the  grain,  the  slower  will  be  the 
inflammation  with  the  same-sized  perforations.  Black  powder  ignites 
very  readily,  which  is  just  the  opposite  of  the  smokeless  powder,  which 
is  now  the  standard  powder  and  which  requires  a  large  amount  of 
flame  to  insure  instantaneous  ignition.  For  this  reason  an  igniting 
charge  of  black  powder  is  put  in  the  base  of  each  section  of  the  charge 
of  smokeless  powder  used  in  large  caliber  guns. 

From  what  has  been  said,  it  can  readily  be  seen  that  a  charge  com- 
posed of  large  grains  will  burn  more  slowly  and  exert  less  strain  on  the 
gun  than  one  composed  of  small  grains.  Hence  the  danger  of  using 
the  same  weight  of  charge  of  black  powder  in  place  of  that  of  smokeless 
powder  or  powder  of  large  grains,  is  obvious. 

The  glazing  of  gunpowder,  which  smooths  and  hardens  the  surface 
of  the  grain,  is  done  to  retard  the  ignition  and  make  it  a  slower-acting 
powder.  Moisture  in  powder  also  reduces  the  rate  of  burning  and  con- 
sequently, the  velocity  and  pressure.  Uniformity  in  size,  shape, 
density,  surface  smoothness,  and  toughness  of  the  grain  are  essential 
in  order  to  obtain  uniform  results  of  velocity.  The  maximum  pressure 
and  muzzle  velocity  are  also  affected  by  the  density  of  loading,  which 
is  fully  defined  in  the  DEFINITIONS. 

It  is  important  that  the  projectile  should  always  be  seated  so  that 
its  base  will  be  at  the  same  distance  from  the  face  of  the  breech,  in 
order  that  the  volume  of  the  powder  chamber  will  be  more  nearly 
constant  for  each  charge.  The  smaller  the  space  the  higher  will  be  the 
initial  velocity  and  the  greater  the  pressure.  Again,  it  is  important 
that  the  powder  charge  for  each  round  fired  should  be  the  same  length. 
The  length  of  the  cartridge  for  any  powder  chamber  should  not  be 
less  than  nine-tenths  (9-10)  the  length  of  the  chamber.  This  is  neces- 
sary in  order  to  eliminate  what  is  known  as  wave  motion.  It  has  been 


GUNNERY  AND  BALLISTICS  93 

found  by  experiment  that  if  a  cartridge  is  much  shorter  than  the 
powder  chamber,  it  is  liable  to  produce  a  motion  of  air  in  the  gases 
formed  in  the  chamber  which  greatly  increases  the  maximum  pressure 
on  the  breech.  It  has  been  found  that  in  long  chambers  wherein 
simultaneous  ignition  and  inflammation  is  difficult,  wave  motion  is 
more  apt  to  occur,  in  which  cases  abnormally  high  local  pressures  have 
been  produced.  It  is  in  order  to  contain  the  required  amount 
of  powder  without  giving  the  chamber  undue  length  that  in  modern 
construction  the  powder  chamber  of  the  guns  have  been  given  greater 
diameter  than  that  of  the  main  bore. 

The  causes  affecting  the  velocity  and  pressure  may  be  summarized 
as  follows:  First,  the  size,  shape,  density,  surface  smoothness,  and 
toughness  of  the  grain.  Second,  the  length  of  the  bore  and  the  con- 
struction of  the  gun.  Third,  the  increase  or  decrease  of  the  weight 
of  the  charge.  Fourth,  the  density  of  loading. 

THE    PROJECTILE    IN    ITS   FLIGHT,    OR  THE    TRAJECTORY 

The  projectile  in  flight  will  be  considered,  for  convenience  of  expla- 
nation: first,  in  the  plane  of  departure,  ignoring  deviating  effects; 
second,  the  entire  trajectory,  including  the -effects  of  wind  and  drift. 

The  projectile  in  its  flight  is  influenced  by:  1.  The  expansive  force 
of  the  powder  gases  which  gives  it  the  initial  velocity  of  translation. 
2.  The  force  of  gravity.  3.  The  resistance  of  the  air.  These  forces 
determine  its  trajectory. 

The  weight  and  dimension  of  the  projectile  as  well  as  the  shape  of 
its  head  also  affect  the  path  of  its  flight,  but  only  because  they  act  upon 
the  retardation  of  the  projectile  due  to  the  resistance  of  the  air. 

Under  the  influence  of  the  expansive  force  of  the  powder  gas  the 
projectile  would  move  with  uniform  velocity  in  a  straight  line  or  in 
continuation  of  the  axis  of  the  bore. 

The  actual  velocity  of  the  projectile  as  it  leaves  the  muzzle  of  the 
gun  is  difficult  to  determine.  It  is,  however,  usually  measured  by 
means  of  an  instrument  called  the  chronograph,  at  some  point  a  short 
distance  from  the  muzzle.  The  velocity  thus  obtained  is  called  in- 
strumental velocity  at  the  point  measured  from  the  muzzle.  By 
means  of  ballistic  formula  this  instrumental  velocity  may  be  reduced 
to  what  it  would  be,  under  the  laws  of  resistance,  at  the  muzzle.  The 
velocity  thus  calculated  is  called  "  muzzle  velocity,"  as  it  is  assumed 
to  be  the  initial  velocity  of  the  projectile  in  the  trajectory.  In  other 
words  it  is  the  velocity,  which  under  the  laws  of  resistance  of  the 


94 


THE  SERVICE  OF  COAST  ARTILLERY 


atmosphere  when  computed  with  ballistic  formula,  would  give  the 
projectile  a  velocity  equal  to  the  instrumental  velocity  at  the  point 
measured  by  the  chronograph. 

If  the  gun  were  fired  where  there  is  no  resistance  to  the  air,  or  in 
vacuo,  and  leaving  out  of  consideration  the  effect  of  gravity,  the  pro- 
jectile would  move  in  a  straight  line  with  uniform  velocity  and  would 
pass  through  equal  distances  for  each  second  of  its  flight.  For  example, 


FIG.  5. 

if  a  projectile  had  an  initial  velocity  of  2,000  feet  per  second,  it  would 
pass  through  2,000  feet  during  each  second  of  its  flight,  or  referring  to 
diagram  (Fig.  5)  it  would  pass  in  each  second  over  OA,  AB,  BC,  these 
distances  being  equal  in  each  case. 

If  the  same  gun  were  fired  in  air,  horizontally,  without  considering 
the  action  of  gravity,  it  would  move  in  the  same  straight  line,  but  the 
distance  passed  over  during  each  successive  second  of  its  flight  would 


FIG.  6. 

gradually  decrease,  that  is,  the  projectile  would  lose  velocity  in  conse- 
quence of  the  resistance  of  the  air.  In  such  a  case  the  distance  passed 
over  during  each  second  of  its  flight  would  be,  referring  to  Fig.  6,  the 
distances  OA,  AB,  BC. 

Under  the  influence  of  gravity  alone  the  space  through  which  the 
projectile  will  fall  in  vacuo  is  determined  by  the  simple  formula: 
Space  (S)  in  feet  equals  one-half  of  the  acceleration  of  gravity  (g), 
mean  value  32.16  feet  per  second,  times,  seconds  squared  (/2),  or  in 


GUNNERY  AND  BALLISTICS 


95 


other  words,  (S  =  %gt2)  a  projectile  will  fall  through  16.08  feet  the  first 
second;  at  the  end  of  the  second  second  the  projectile  will  have  fallen 
64.32  feet;  at  the  end  of  the  third,  144.72  feet,  and  at  the  end  of  the 
fourth,  257.28  feet.  Therefore,  if  the  same  gun  were  fired  in  air 
horizontally,  the  projectile  is,  due  to  the  influence  of  gravity,  drawn 
towards  the  center  of  the  earth  with  a  uniformly  accelerated  velocity, 


and  disregarding  the  retardation  due  to  the  resistance  of  the  air  in 
falling  the  projectile  would  be,  referring  to  Fig.  6,  at  points  a,  b,  c,  in 
its  path,  instead  of  at  the  points  A,  B,  C,  referred  to  in  Fig.  5. 

In  the  air  the  projectile  is  retarded  in  its  fall  by  the  resistance 
offered  to  it  which  would  tend  to  retard  it,  so  that,  strictly  speaking, 


the  distances  given  above  are  not  absolutely  correct.  However,  due 
to  the  small  velocity  of  fall  obtained  in  direct  fire,  the  errors  are  so  small 
that  they  may  be  disregarded.  Therefore,  under  the  conditions  of  the 
initial  velocity,  force  of  gravity,  and  resistance  of  the  air,  the  path  of 
the  projectile  disregarding  drift  and  wind,  would  be  as  shown  in  Fig.  8. 
The  resistance  which  the  air  offers  to  the  projectile  is  proportional 
to  the  cross-sectional  area  exposed,  and  the  square  of  the  velocity. 


96 


THE  SERVICE   OF  COAST  ARTILLERY 


Referring  to  figures  7,  8  and  9  it  is  evident  that  a  gun  may  be  fired 
so  as  to  produce  trajectories  similar  to  those  illustrated,  that  is:  First, 
the  trajectory  which  is  entirely  above  the  horizontal  plane,  or  where 
the  target  is  above  the  level  of  the  horizontal  plane,  passing  through 
the  muzzle;  second,  where  the  target  is  on  a  level  with  the  plane, 
passing  through  the  muzzle,  and  third,  where  the  target  is  below 
the  horizontal  plane,  passing  through  the  muzzle,  which  is  the  usual 
trajectory  found  in  practice. 

In  order  that  the  terms  may  be  thoroughly  understood,  the  different 
elements  of  the  trajectory  are  indicated. 

The  horizontal  trajectory  is  the  one  considered  in  all  fundamental 
ballistic  computations.  It  is  very  seldom,  in  actual  practice,  that  the 
target  is  in  the  initial  plane;  therefore,  the  trajectory  most  commonly 
found  in  practice  is  the  trajectory  described  where  the  target  is  below 
the  horizontal  plane  passing  through  the  axis  of  the  gun.  It  is  there- 


\^fftifht  of   &•"* 


Water  Level 


FIG.  9. 

fore  evident  that  some  means  of  applying  the  computations  for  the 
horizontal  trajectory,  or  the  values  given  in  the  range  table,  must  be 
devised  to  apply  to  the  trajectory  in  the  three  cases  heretofore  men- 
tioned. This  is  accomplished  by  a  method  known  as  the  principle  of 
rigidity  of  the  trajectory,  which  may  be  defined  as  follows:  The  prin- 
ciple of  the  rigidity  of  the  trajectory  assumes  that  the  relations  existing 
between  the  elements  of  the  trajectory  and  the  chord  representing  the 
range  are  sensibly  the  same,  whether  the  latter  be  horizontal  or  inclined 
to  the  horizon. 

The  acceptance  of  this  principle  assumes  that  knowing -the  angle  of 
departure  necessary  to  hit  a  certain  point  at  a  horizontal  range  "  X  " 
from  the  gun  and  on  the  same  level,  the  angle  of  departure  necessary 
to  hit  a  certain  point  "  h  "  feet  below  the  level  of  the  gun  would  be 
obtained  by  subtracting  the  value  of  the  position  angle  from  the 
angle  of  departure  of  the  horizontal  trajectory. 


GUNNERY  AND  BALLISTICS  97 

Likewise  if  the  target  is  above  the  level  of  the  gun  the  position 
angle  would  be  added  to  the  angle  of  departure  of  the  horizontal 
trajectory.  Both  of  these  are  shown  graphically  in  Figs.  7  and  9. 

The  power  of  a  projectile  to  overcome  the  resistance  of  the  air  is 
dependent  upon  its  weight,  dimensions,  and  shape  of  its  head.  It  is  a 
well-known  fact  that  given  two  balls,  one  a  baseball,  and  one  a  light 
hollow  rubber  ball  of  the  same  size,  the  heavy  ball  can  be  thrown 
further  than  the  light  ball.  This  is  because  its  greater  weight  gives  it 
more  power  to  overcome  the  resistance  of  the  air.  If  the  two  balls 
were  of  the  same  weight,  one  being  larger  than  the  other,  the  larger  ball 
would  meet  with  more  resistance  than  the  smaller  one  because  there 
would  be  more  surface  exposed  to  the  resistance  of  the  air.  Applying 
this  principle  to  ballistics,  a  number  is  given,  known  as  the  ballistic 
coefficient,  which  expresses  the  power  of  a  projectile  to  overcome  the 

resistance  of  the  air.     It  is  expressed  by  C=/—   -  in  which  delta  sub 

oca2 

one  is  the  standard  density  of  the  air;  delta,  the  density  of  the  air 
when  firing;  w,  the  weight  of  the  projectile  in  pounds;  c,  the  coefficient 
of  reduction,  depending  for  its  value  upon  the  smoothness  of  the  pro- 
jectile and  its  steadiness  in  flight;  and  d,  the  diameter  of  the  projectile 
in  inches;  /  is  known  as  the  altitude  factor.  Two  other  factors  are 
frequently  introduced  into  the  equation  in  order  to  account  for  the 
increased  wind  effect  on  the  projectile  as  it  rises,  indicated  by  the  symbol 
fw  and  may  be  either  negative  or  positive  depending  upon  whether  a 
rear  or  head  wind  component  is  considered.  The  other  factor  is  known 
as  the  reducing  factor,  which  takes  into  account  the  oblique  presentation 
of  the  projectile  to  the  resistance  of  the  air;  this  factor  is  expressed  by 
the  Greek  letter  "gamma"  (f)  and  its  value  is  based  upon  experimental 

firings.     The  complete  coefficient  then  becomes  C  =  -^-fa-fw . 

For  similar  projectiles,  that  is,  projectiles  which  have  proportional 
dimensions  and  the  same  shape  head,  the  ballistic  coefficient  is  directly 
proportional  to  the  weight  of  the  projectile  and  inversely  proportional 
to  the  area  of  cross-section,  or  is  proportional  to  the  square  of  the 
diameter;  that  is,  C=W,  divided  by  D  squared. 

It  is  a  well-known  fact  that  a  long-tapered  tool  can'  be  forced  into  a 
resisting  medium  more  readily  than  one  having  a  shorter  taper;  that 
is,  the  sharper  the  instrument,  the  less  power  it  requires  to  force  it 
through  the  medium.  This  same  principle  is  true  of  projectiles  passing 
through  the  air — the  longer  the  taper  of  the  head,  the  less  power  required 
to  force  it  through  the  air,  because  the  area  exposed  to  the  resistance  of 


98  THE  SERVICE  OF  COAST  ARTILLERY 

the  air  is  less.  We  may,  therefore,  consider  that  the  sharpening  of  the 
head  of  a  projectile  increases  its  power  to  force  its  way  through  the  air, 
which  is  equivalent  to  increasing  its  weight. 

The  coefficient  of  form,  represented  by  "  c"  is  usually  taken  as 
unity,  and  depends  for  its  value  upon  the  results  of  experimental 
firings. 

Should  a  projectile  not  keep  its  head  on  in  flight,  the  value  "  c" 
would  necessarily  be  greatly  increased  above  unity,  and  therefore, 
decrease  the  ballistic  coefficient,  or  decrease  the  projectile's  power  to 
overcome  the  resistance  of  the  air. 

Considering  now  the  deviating  effects  upon  a  proj  ectile  in  its  flight, 
which  are  those  due  to  drift  and  wind,  we  find  that  the  path  of  the  pro- 
jectile, instead  of  being  as  shown  in  Fig.  6,  or  lying  in  the  vertical 
plane  of  departure,  describes  a  curve  of  double  curvature,  the  horizontal 
projection  of  which  is  shown  in  plan  in  Fig.  10.  The  only  case  in  which 
the  projectile  would  remain  in  the  plane  of  departure  is  when  the  wind 
exactly  equaled  the  deviating  effect,  due  to  drift.  The  first  deviating 


•Horizontal  projection. 
FIG.  10. 

effect,  or  that  of  drift,  is  due  to  rifling  of  the  gun,  which  causes  the  pro- 
jectile upon  leaving  the  muzzle,  to  drift  to  the  right  for  guns  witn  the 
twist  of  rifling  to  the  right. 

The  wind  has  considerable  effect  upon  the  flight  of  projectiles.  In 
the  United  States  coast  artillery  service  it  may  be  designated  in  two 
ways:  First,  by  its  azimuth,  and  second,  by  what  is  known  as  the 
"  clock  convention."  That  is,  a  wind  blowing  from  the  west  is  said  to 
have  an  azimuth  of  90  degrees;  a  north  wind,  an  azimuth  of  180  degrees. 
The  clock  convention  refers  the  wind  to  the  line  of  direction;  that  is, 
the  observer  is  suppqsed  to  be  at  the  center  of  a  clock  dial,  the  figure 
12  pointing  towards  the  target.  A  head  wind  is  known  as  a  12-o'clock 
wind;  a  rear  wind,  as  a  6-0' clock  wind;  a  wind  directly  from  the  right, 
as  a  3-o' clock  wind;  and  a  wind  from  the  left,  as  a  9-o' clock  wind,  and 
so  on,  the  entire  circle  being  divided  into  12  sections,  following  the 
known  figures  of  the  clock  dial.  The  direction  of  the  wind  as  sent  to 
each  primary  station  is  given  in  azimuth  by  means  of  the  aeroscope. 

The  effect  of  the  wind  upon  a  projectile  is  directly  proportional  to 
the  wind  velocity;    that  is,  if  a  one-mile  wind  will  shorten  the  range 


GUNNERY  AND  BALLISTICS  99 

5  yards,  a  ten-mile  wind  will  shorten  it  ten  times  as  much,  or  50  yards. 
Again,  if  a  one-mile  wind  will  cause  the  projectile  to  deviate  3  yards  to 
the  right  or  left,  a  ten-mile  wind  will  cause  the  same  projectile  to  deviate 
approximately  30  yards.  The  effect  of  a  head  or  retarding  wind  is  to 
shorten  the  range.  A  wind  blowing  in  the  direction  of  the  range, 
that  is,  a  6-o'clock  wind,  would  tend  to  increase  the  range.  A  3-o'clock 
wind  would  cause  the  projectile  to  deviate  to  the  left,  and  a  9-o' clock 
wind  to  deviate  to  the  right.  A  wind  blowing  from  any  other  direction 
than  those  stated  would  cause  a  change  in  range  and  deviation. 
In  such  cases,  it  is  necessary  to  determine  the  component  of  the  wind's 
velocity  which  affects  the  range,  and  also  the  component  which  would 
cause  it  to  deviate.  The  component  which  affects  the  range  and  which 
is  parallel  to  the  line  of  direction,  is  called  the  range  component;  while 
that  component  which  acts  at  right  angles  to  the  line  of  direction  is 
known  as  the  deviating  component.  The  range  component  of  a  1 
o'clock  wind,  for  example,  is  87  per  cent,  of  the  wind's  velocity;  the 
deviating  component  is  50  per  cent,  of  the  wind's  velocity.  That  is,  if  a 
wind  had  a  velocity  of  20  miles  per  hour,  its  range  component  would  be 
17  miles  per  hour  and  its  deviating  component  would  be  10  miles  per 
hour.  The  velocity  of  the  wind  is  determined  by  an  instrument  called 
the  anemometer. 


AIMING  AND  LAYING 

In  order  to  give  a  gun  the  direction  and  elevation  necessary  to  hit 
the  target,  it  must  be  properly  aimed,  or  laid  to  the  data  previously 
determined  by  the  methods  hereafter  outlined.  The  term  "  aiming  " 
will  be  employed  when  using  the  sights,  and  "  laying  "  when  the  gun  is 
given  direction  by  means  of  the  azimuth  circle,  and  elevation  by  means 
of  the  elevation  scale  or  quadrant.  The  three  cases  of  pointing  are  as 
follows : 

Case  I. — When  direction  and  elevation  are  both  given  by  the  sight. 
In  this  case  the  sight  is  placed  on  the  gun  trunnions. 

This  method  is  used  only  with  rapid-fire  guns  not  provided  with 
quadrant-range  scales.  In  using  the  sight  the  gun  pointer  for  the  first 
shot  sets  the  elevation  scale  to  the  deflection  ordered.  He  observes  the 
splash  caused  by  the  shot  and  corrects  the  deflection  for  the  next  shot. 
This  is  done  by  keeping  the  vertical  hair  on  the  designated  point  on  the 
target  by  traversing  the  carriage  until  the  shot  strikes  and  then  bisecting 
the  splash  with  the  vertical  hair  by  turning  the  deflection  screw.  The 
difference  between  the  readings  of  the  deflection  scale  after  bisecting 


100  THE  SERVICE  OF  COAST  ARTILLERY 

on  the  splash  and  the  original  reading  then  gives  the  error  made,  and 
the  setting  in  deflection  should  be  corrected  accordingly.  The  vertical 
wire  is  then  brought  back  to  the  target  by  traversing  the  carriage. 

Case  II. — When  direction  is  given  by  the  sight  and  elevation  by  the 
range  scale  on  the  carriage. 

The  sight  in  this  case  is  placed  upon  the  bracket  on  the  sight 
standard.  It  is  the  normal  method  used  with  guns  of  the  primary 
and  usually  intermediate  armament.  Corrected  ranges  are  sent  to  the 
guns  for  the  next  bell  every  fifteen  seconds  and  the  range  scale  set 
accordingly  by  the  range  setter.  The  gun  pointer  keeps  the  sight  set 
at  the  deflection  received  from  the  plotting  room  until  after  the  first 
shot,  and  traverses  or  directs  the  traversing  so  as  to  keep  the  vertical 
wire  on  the  target.  With  the  disappearing  carriage  the  traversing  is 
stopped  long  enough  for  the  projectile  to  be  put  in  the  gun.  The  gun 
pointer  fires  or  gives  the  command  "  fire,"  and  then  observes  the  fall 
of  his  shot  and  corrects  the  deflection  as  previously  explained,  unless 
otherwise  ordered  by  the  battery  commander. 

Case  III. — When  direction  is  given  by  laying  the  gun  in  azimuth  by 
the  azimuth  circle,  and  the  elevation  by  quadrant  or  range  scale  on  the 
carriage. 

This  case  is  used  for  mortars,  and  for  guns  when  conditions  are  such 
as  to  prevent  the  using  of  Case  II. 


ACCURACY    OF   FIRE    AND   PRACTICE 

Accuracy  of  fire  depends  upon:  1.  The  accuracy  of  the  gun. 
2.  The  uniform  action  of  the  carriage  during  recoil.  3.  The  uniform 
action  of  the  powder.  4.  The  uniform  weight  of  the  projectile.  5. 
The  uniformity  of  loading. 

Accuracy  of  practice  depends  upon:  The  accurate  working  of  the 
personnel:  (a)  Correct  location  of  the  target.  (6)  Accuracy  of  cor- 
rections for  wind,  drift,  travel  of  target  and  conditions  of  the  atmosphere, 
etc.  (c)  Accuracy  of  the  gun  pointer  and  range  setter,  (d)  Correct 
judgment  upon  observation  of  fire. 

From  the  above  it  is  readily  seen  that  the  "  accuracy  of  fire  "  is 
measured  by  the  mean  distance  -of  the  points  of  impact  of  all  the  shots 
in  a  group  from  the  center  of  impact,  or  the  center  of  the  points  of 
impact  of  the  group  of  shots,  while  the  "  accuracy  of  practice  "  is 
measured  by  the  distance  of  the  center  of  impact  from  the  center  of  the 
target.  For  example: 


GUNNERY  AND  BALLISTICS  101- 

Five  shots  are  fired  at  a  fixed  target  at  a  range  of  7,000  yards. 
The  shots  all  fall  within  a  rectangle  10  yards  long  and  5  yards  wide, 
and  the  average  distance  of  the  five  shots  from  the  target  is  200  yards 
short  and  5  yards  right. 

The  accuracy  of  fire  was  excellent,  but  the  accuracy  of  practice 
very  poor. 

Ballistic  Symbols  and  Simple  Formulas. 

/.  s.  stands  for  "  foot-seconds,"  which  is  the  unit  of  measure  for 
velocities.  For  example:  32.16  f.  s.  is  read  32.16  foot-seconds,  and 
means  that  the  body  considered  is  moving  at  the  rate  of  32.16  feet 
per  second. 

w  (small  w)  means  "  weight/'  and  in  ballistic  formulas  stands  for 
the  weight  of  the  projectile  in  pounds. 

d  (small  d)  means  "  diameter,"  and  in  ballistic  formulas  stands  for 
the  diameter  or  caliber  of  the  projectile  in  inches. 

#1  (delta  sub  one)  stands  for  the  density  of  the  air  two-thirds 
saturated  with  -moisture,  at  standard  temperature  and  barometric 
pressure,  usually  taken  at  60°  F.  and  barometer  30  inches. 

F  written  after  figures  denoting  temperature  means  "Fahrenheit," 
which  is  the  name  given  to  the  kind  of  thermometer  in  common  use 
in  this  country.  60°  F.  therefore  is  read  sixty  degrees  Fahrenheit. 

d  (delta)  stands  for  the  density  of  air,  two-thirds  saturated  with 
moisture,  for  the  readings  of  the  thermometer  and  barometer  taken 
at  the  time  of  firing  the  particular  shot  under  consideration. 

<N 

-4  is  read  delta  sub  one  divided  by  delta,  and  means  the  density  of 

standard  air  divided  by  the  density  of  air  at  the  time  of  firing  the 
shot. 

A  coefficient  is  a  number  written  before  any  symbol  to  indicate  how 
many  times  the  symbol  is  to  be  taken.  Thus,  2g  means  twice  gravity, 
or  2X32.16  =  64.32. 

c  (small  c)  in  ballistic  formulas  is  called  the  "  Coefficient  of  Reduc- 
tion or  Form."  It  is  introduced  in  order  to  convert  the  result  obtained 
for  a  projectile  of  a  particular  form  to  that  for  a  projectile  of  some 
other  form  and  is  determined  by  experiment. 

C  (large  C)  in  ballistic  formulas  is  called  the  "  Ballistic  Coefficient" 
It  depends  upon  the  density  of  the  air  and  the  weight,  diameter,  and 

form  of  the  projectile,  and  might  be  written  -^  --^  (omitting  reference 


102  THE  SERVICE  OF  COAST  ARTILLERY 

to  altitude,  wind  and  reducing  factors).  This  last  expression  is  read, 
delta  sub  one  divided  by  delta,  multiplied  by  w  divided  by  cd2,  which 
means  density  of  standard  air  divided  by  density  of  the  air  at  the  time 
of  firing,  multiplied  by  the  weight  of  the  projectile  in  pounds  divided  by 
the  coefficient  of  reduction  multiplied  by  the  square  of  the  diameter  of  the 
projectile  in  inches. 

V  (large  V)  stands  for  muzzle  velocity.  That  is,  the  number  of 
feet  per  second  at  which  the  projectile  is  moving  when  it  leaves  the 
muzzle. 

v  (small  v)  stands  for  the  velocity  in  f.  s.  of  the  projectile  at  any 
point  of  its  trajectory. 

Va)  (v  sub  omega)  stands  for  the  velocity  in  f.  s.  at  the  point  of 
fall. 

i?o  (v  sub  zero)  stands  for  the  velocity  in  f.  s.  at  the  summit  of  the 
trajectory. 

cf)  (phi)  stands  for  the  angle  of  departure  of  the  projectile. 

6  (theta)  stands  for  the  angle  which  the  tangent  to  the  trajectory 
at  any  point  makes  with  the  horizontal.  In  the  ascending  branch  this 
angle  will  always  open  outward  from  the  gun,  and  will  therefore  be  re- 
garded as  positive.  At  the  summit  of  the  trajectory  the  tangent  will 
be  horizontal,  and  theta  will  therefore  become  zero.  In  the  descending 
branch  the  angle  will  open  inward,  that  is,  towards  the  gun,  and  will 
therefore  be  regarded  as  negative. 

w  (omega)  represents  the  angle  of  fall,  that  is,  the  angle  at  which 
the  projectile  strikes  the  horizontal  plane  passing  through  the  muzzle 
of  the  gun.  The  angle  of  fall  (aj)  is  always  greater  than  the  angle  of 
departure  (</>). 

x  (small  x)  represents  the  horizontal  distance  from  the  muzzle  to 
any  point  within  the  range  of  the  projectile. 

y  (small  y)  represents  the  height  of  the  projectile  above  the  horizontal 
plane  passing  through  the  muzzle  of  the  piece  at  any  point  of  the 
trajectory. 

x  and  y  are  called  the  co-ordinates  of  any  point  of  the  trajectory, 
x  representing  the  horizontal  distance  of  the  point  from  the  muzzle 
of  the  piece,  and  y  its  vertical  distance  above  the  horizontal  plane 
passing  through  the  muzzle,  x  is  known  as  the  abscissa  of  the  point, 
and  y  as  the  ordinate.  Taken  together  they  are  called  the  coordinates 
of  the  point. 

X  (large  X)  represents  the  horizontal  range,  that  is,  the  distance 
from  the  muzzle  to  the  point  where  the  projectile  first  grazes  the  hori- 
zontal plane  passing  through  the  muzzle. 


GUNNERY  AND  BALLISTICS  103 

T  (large  T)  represents  the  time  of  flight  in  seconds,  that  is,  the 
time  it  takes  the  projectile  to  travel  from  the  muzzle  to  the  point  where 
it  first  grazes  the  horizontal  plane  passing  through  the  muzzle.  It  is 
the  "  T  "  for  the  range  X. 

t  (small  t)  represents  the  time  of  flight  to  any  point  within  the  range 
of  the  projectile.  It  is  the  "  t  "  for  the  range  x. 

E  (large  E)  stands  for  the  energy  of  the  projectile  in  foot -tons. 
It  is  equal  to  the  weight  of  the  projectile  in  pounds  multiplied  by  the 
square  of  its  velocity  and  divided  by  4480  times  gravity.  The  equation 

r> 

being  E=  foot-tons. 

A  TTOvJw 

TT  (pi)  represents  the  ratio  between  the  diameter  and  the  circum- 
ference of  a  circle.  It  is  equal  to  3.1416. 

e  (small  e)  represents  the  energy  of  a  projectile  per  inch  of  circum- 
ference.    It    sometimes    appears    in    problems    of    penetration.     The 

wife 
equation   is   0=777^ foot-tons,   which   may  be   thus   interpreted: 

Energy  per  inch  of  circumference  equal  to  weight  of  projectile  X  square 
of  its  velocity,  and  divided  by  4480  X 3. 141 6  X diameter  of  projectile  X 
32.16. 

W  (large  W)  stands  for  the  velocity  of  the  wind  in  f.  s. 

Wx  (read  W  sub  x)  represents  the  velocity  of  the  wind  parallel 
to  the  range. 

Wy  (read  W  sub  ~y)  represents  the  velocity  of  the  wind  normal, 
that  is,  at  right  angles  to  the  range. 

u  (small  u)  represents  the  horizontal  progress  of  the  projectile 
in  f.  s. 

p  (rho)  represents  the  resistance  of  the  air  to  the  motion  of  the 
projectile  in  pounds. 

T  (tau)  stands  for  the  thickness  of  armor  in  inches. 
fa  (small  f  sub  a)   represents  the  altitude  factor  and  depends  for 
its  value  upon  the  height  the  projectile  rises  above  the  level  of  the 
gun. 

fw  (small  f  sub  w)  represents  the  wind  factor  and  takesin  to  con- 
sideration the  effect  of  the  wind  on  the  projectile  as  it  rises. 

?/o  (small  y  sub  zero)  represents  the  maximum  ordinate  or  height 
in  feet  to  summit  of  trajectory. 

Z,  A,  Log  B',  T'  and  LogV  are  functions  from  Table  II,  Artillery 
Circular  M. 


104  THE  SERVICE  OF  COAST  ARTILLERY 

FORMULAS 
For  use  with  Table  II,  Artillery  Circular  M. 


»= 

7     *- 

; 


=  v     cos  10  sec 


?/o  =  a"oC  tan 
tan  aj  =  B'  tan  < 


W  COS  0 

w  =  -  L  =  u  cos  o  sec  w  : 


cos 


4480^' 


For  a  given  weight  of  charge  the  velocity  increases  slightly  with 
the  temperature  of  the  powder  at  the  instant  of  firing,  and  for  a  given 
increase  of  temperature  this  increase  in  velocity  varies  with  the  initial 
velocity. 

For  all  lots  of  powder  tested  recently  the  charges  have  been  adjusted 
to  give  the  prescribed  velocities  when  fired  at  the  standard  temperature 
of  70°.  In  the  earlier  tests  only  the  temperature  of  the  air  was  recorded, 
and  for  these  lots  but  slight  error  will  result  from  taking  this  as  the 
temperature  of  the  powder. 

According  to  the  data  available  at  present,  the  following  table  gives 
the  corrections  for  temperature. 


GUNNERY  AND  BALLISTICS 


105 


I 

Normal  Initial  Velocities. 

1 

833 

917 

980 

1056 

1148 

1220 

2000 

2100 

2150 

2200 

2250 

2400 

2600 

10 

27 

30 

32 

34 

38 

40 

65 

67 

69 

71 

72 

77 

84 

0 

26 

29 

31 

33 

37 

39 

63 

66 

67 

69 

70 

75 

81 

To    be 

10 

25 

28 

29 

31 

35 

37 

60 

62 

64 

66 

67 

71 

77 

deducted 

20 

23 

26 

27 

29 

32 

34 

55 

58 

59 

61 

62 

66 

71 

^  fromnor- 

30 

20 

23 

24 

25 

29 

30 

49 

51 

53 

54 

55 

59 

64 

(mal     ini- 

40 

17 

19 

20 

21 

24 

25 

41 

43 

44 

46 

46 

49 

53 

t  i  a  1  ve- 

50 

13 

14 

15 

16 

18 

19 

30 

32 

33 

34 

34 

36 

39 

locity. 

60 

7 

8 

8 

9 

10 

10 

17 

18 

18 

19 

19 

20 

22 

• 

70 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

1      To    be 

80 

9 

9 

10 

11 

12 

13 

21 

22 

22 

23 

24 

26 

28 

added  to 

90 

19 

21 

22 

24 

26 

28 

46 

48 

50 

50 

52 

56 

60 

normal 

100 

32 

35 

37 

41 

44 

47 

77 

81 

82 

84 

87 

92 

100 

initial 

velocity. 

NOTE — This  table  applies  to  lots  tested  at  a  temperature  of  70°. 


A  cute  Angle  Obtuse  Angle 


A  BD  =  Right  Angle 


Parallel  Lines 


B1  Primary  Station 
B"Secondary  Station 


Parallel  Lines 


-§" 


CB  &AB  'Perpendicular 
Lines  A 

/     \      Triangles 


Sea/en*   \^      //sosce/es\       / Eauilot0raf\       /Isosceles 


Acute  Angled  Triangles  ffight  AngledTriangles         Obtuse  Angled  Triangles 

Polygons 


Triangle  Square  _  Hexagon  Octagon     Concentric  Circles   ELLIPSE  (Elliptical') 

ADBE 'Circumference  •*.*  Angle 


Azimuth  angles  are 
measured  from  the 
South  O°ina  clock- 
wise directi'on.as 
angle  OA'/IO' 


ADorBD'Arc 

orCBorCD- Radius        ^      Chord- BP    D,am-BOC~        Arc -AC 
X  y-  Opposite  Angles 
D/ometer 


Quadrangular  Cylinder          Cylindro-Conicle 


A*  Fulcrum       W- Weight 


B  ere/ Gear 


Spur  P.  ing 


Inferno/ or Angu/ar  GearWhee/' 


FIG.  10a. — Geometrical  Magnitudes,  Etc. 


106 


CHAPTER  V 
ARMAMENT 

THE  seacoast  armament  of  the  United  States  is  a  development  of  the 
last  twenty-five  years.  The  construction  of  the  first  type  of  8-inch 
breech-loading  rifle  for  coast  defense  purposes  was  undertaken  in  1883 
and  completed  at  the  West  Point  foundry  three  years  later.  In  1888 
Congress  began  making  appropriations  for  seacoast  armament  and  has 
continued  the  policy  ever  since.  The  present  system  of  coast  defense 
is  the  result. 

All  the  large-caliber  guns  now  mounted  have  been  designed,  manu- 
factured and  mounted  since  1888.  In  fact,  it  was  not  until  1895  that 
the  modern  material  began  to  be  turned  over  to  the  coast  artillery,  and 
the  greater  part  of  the  present  armament  has  been  installed  since 
1897. 

The  United  States  has  been,  until  recently,  wedded  to  built-up  gun 
construction  of  steel  forgings.  Of  late,  however,  the  Ordnance  Depart- 
ment has  taken  up  the  manufacture  of  the  wire-wound  type  of  built-up 
gun  and  is  at  present  manufacturing  a  14-inch  rifle  of  that  type. 

Designs  of  a  6-inch  wire-wrapped  rifle  and  a  new  design  of  12-inch 
wire-wrapped  mortar  were  recently  completed.  In  the  case  of  the 
mortar  the  employment  of  the  wire  wrapping  is  said  to  decrease  the 
weight  by  something  like  30  per  cent ;  while  the  cost  is  greatly  reduced 
by  the  fact  that  the  cost  of  the  wire  per  pound  is  less  than  one-half 
that  of  steel  forgings  which  it  replaces.  The  new  mortars  have  a  breech 
mechanism  similar  to  that  of  the  later  seacoast  rifles,  which  will  greatly 
increase  the  rapidity  of  loading. 

The  disappearing  carriage  system  was  adopted  by  the  Endicott 
Board  in  1886,  after  exhaustive  inquiry  and  careful  consideration  by 
the  officers  who  composed  it.  It  was  later  accepted  by  the  joint  com- 
mittee of  Congress  that  had  the  general  subject  of  coast  defense  in 
charge.  The  disappearing  system  has  always  challenged  that  of  the 
barbette  on  two  important  points :  First,  that  of  the  protection  afforded 
the  gun,  its  carriage  and  personnel.  Second,  inability  to  discover  the 
position  of  batteries  until  they  open  fire.  While  the  disappearing  sys- 

107 


108  THE  SERVICE   OF  COAST  ARTILLERY 

tern  has  these  advantages,  its  cost  is  greatly  in  excess  of  that  of  the 
barbette  system,  to  say  nothing  of  the  difference  in  the  care  and  atten- 
tion required  by  the  two  types. 


COAST    ARTILLERY    ARMAMENT 

Coast  artillery  armament  is  classified  as  PRIMARY,  INTERMEDIATE, 
and  SECONDARY. 


PRIMARY   ARMAMENT 

16-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1895 

The  general  drawing,  Fig.  1,  indicates  the  method  of  construction. 
A  series  of  this  type  of  gun  was  recommended  by  the  Endicott  Board 
for  the  defense  of  the  harbors  of  New  York,  San  Francisco,  Boston  and 
Hampton  Roads.  In  point  of  energy  and  range  it  is  the  largest  gun 
in  the  world. 

It  is  of  the  built-up  forged-steel  type  and  consists  of  a  tube,  jacket, 
2  C  hoops,  3  B  hoops,  1  D  hoop,  trunnion  band  or  hoop,  trunnion  rim- 
bases,  Creech  plate,  breech-block,  breech  bushing,  screw  box,  copper 
rotating  ring,  powder  chamber,  forcing  cone,  centering  slope,  shot 
chamber  and  main  bore. 

The  breech  mechanism  (Stockett)  is  practically  the  same  as  that  of 
the  10-inch  rifle,  model  of  1895,  shown  in  Fig.  13,  except  in  dimensions; 
the  breechblock  having  a  diameter  of  26  inches  and  total  length  of  27 
inches.  The  threaded  portion  is  divided  into  12  sectors,  six  threaded 
and  six  slotted,  each  sector  being  30  degrees  and  corresponding  to  sim- 
ilar sectors  in  the  breech  recess;  the  rotating  and  translating  racks  are 
cut  out  of  a  solid  block,  the  console  or  tray  is  made  of  cast  steel.  The 
bore  has  96  grooves,  twist  of  rifling  one  turn  in  50  calibers  to  one  turn 
in  25  calibers. 

Total  length  591  inches,  with  a  diameter  at  the  breech  of  60  inches, 
gradually  diminishing  to  28  inches  at  the  muzzle.  Weight  127  'tons; 
length  of  bore  35  calibers;  weight  of  projectile,  capped,  2,400  pounds; 
weight  of  propelling  charge,  nitro-cellulose  powder,  612  pounds;  weight 
of  bursting  charge,  high  explosive,  for  A.P.  shot,  46.1  pounds;  for 
A.P.  shell,  139.3  pounds. 

Muzzle  velocity  2,150  foot-seconds.  Muzzle  energy  76,904  foot- 
tons.  Maximum  pressure  38,000  pounds  per  square  inch.  Maximum 
elevation  permitted  by  the  carriage  15  degrees,  corresponding  range 


ARMAMENT  '  109 

15,558  yards.     Penetration  Krupp  cemented  armor,  normal  impact  at 
muzzle,  42  inches. 

Only  one  gun  of  this  type  has  been  built  and  it  has  never  been 
permanently  mounted. 

14-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1907 

Guns  of  this  caliber  were  recommended  by  the  Chief  of  Ordnance 
in  1906,  based  upon  the  recommendation  of  the  National  Coast 
Defense  Board,  which  consisted  of  officers  of  the  army  and  navy.  The 
question  of  erosion  as  affecting  the  accuracy  and  life  of  seacoast  cannon 
caused  the  Ordnance  Department  to  consider  means  of  increasing  the 
caliber  of  high-power  guns  and  decreasing  the  velocities  used,  at  the 
same  time  retaining  the  maximum  gun  power  or  increasing  it.  The 
importance  of  these  deliberations  may  be  understood  when  it  is  stated 
that  the  12-inch  B.L.  rifls,  Model  of  1900,  with  a  muzzle  velocity  of 
2,500  feet  per  second,  is  not  expected  to  last  through  an  engagement  of 
more  than  one  and  one-half  hours'  duration,  assuming  that  the  rate  of 
fire  permissible  with  this  piece  is  used,  this  result  being  due  to  the 
rapid  rate  at  which  the  bore  is  worn  away  under  high  conditions  of 
loading  and  firing. 

It  was  therefore  decided  that  in  order  to  meet  the  evil  effects  of  this 
gun  erosion,  high  velocities  and  heavy  powder  pressures  should  be 
abandoned,  and  return  made  to  the  custom  of  firing  heavier  projectiles 
with  smaller  velocities,  at  the  same  time  retaining  equal  or  greater 
gun  power.  It  may  thus  be  seen  that  the  larger  caliber  gun  was  only 
decided  upon  after  considerable  experience  and  careful  study  on  the 
part  of  the  Ordnance  Department. 

It  may  be  said  in  connection  with  the  above,  that  it  is  entirely 
feasible  to  reline  guns,  but  the  cost  of  inserting  new  liners  is  consider- 
able, especially  when  it  is  observed  that  the  guns  have  to  be  dismounted 
and  transported  from  their  position  in  coast  forts  to  some  ordnance 
arsenal,  where  the  work  of  relining  is  done. 

The  14-inch  gun  is  designed  primarily  for  the  defense  of  wide  channels 
and  harbors  where  the  highest  gun  power  is  required.  Its  general 
construction  and  nomenclature  are  practically  the  same  as  that  of  the 
12-inch  B.L.  Rifle.  The  muzzle  velocity  is  2,100  foot-seconds.  Pene- 
tration in  Krupp  armor,  normal  impact  at  §,500  yards,  12  inches.  The 
life  of  this  gun  with  the  muzzle  velocity  indicated  may  be  taken  at  10 
years,  with  the  regular  service  practice  firing. 


110  THE  SERVICE  OF  COAST  ARTILLERY 


12-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1888 

This  rifle  follows  the  general  method  of  built-up  forged  steel  con- 
struction. It  consists  of  the  tube,  jacket,  6  C  hoops,  2  D  hoops,  4  B 
hoops,  5  A  hoops  and  other  parts  as  indicated  in  Fig.  1 . 

The  breech  mechanism  (interrupted  screw  system)  is  the  same  as 
that  of  the  10-inch  rifle,  model  of  1888;  except  in  dimensions,  and  that 
roller  or  ball  bearings  are  introduced  into  the  tray  hinge,  to  carry 
easily  the  greater  weight.  The  bore  has  72  grooves,  twist  of  rifling, 
one  turn  in  50  calibers  to  one  turn  in  25  calibers. 

Total  length  439.9  inches;  weight  52  tons;  length  of  bore  34 
calibers;  weight  of  projectile,  capped,  1,046  pounds;  weight  of  pro- 
pelling charge,  nitro-cellulose  powder,  268  pounds;  weight  of  igniter 
charge  7  pounds;  weight  of  bursting  charge,  gun  cotton,  for  A. P. 
shot,  13  pounds;  for  A.P.  shell,  39.4  pounds. 

Muzzle  velocity  2,250  foot-seconds.  Muzzle  energy  36,824  foot- 
tons.  Maximum  pressure  38,000  pounds  per  square  inch.  Maximum 
range  15,134  yards.  Penetration  in  Krupp  cemented  armor,  at  5,000 
yards,  13  inches. 


12-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1888,  Mi 

This  rifle  is  similar  in  construction  and  power  to  the  original  model, 
except  that  it  has  5  C  hoops,  2  D  hoops,  3  B  hoops  and  4  A  hoops. 
Only  a  few  of  this  modification  were  made. 


12-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1888,  MiJ 

This  rifle  is  similar  in  construction  and  power  to  the  original  model, 
except  that  it  has  3  C  hoops,  1  D  hoop,  3  B  hoops  and  3  A  hoops. 

Total  length  442.56  inches;  weight  51  tons;  length  of  bore  35 
calibers. 

Maximum  range  11,636  yards. 


12-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1888,  Mn 

This  rifle  is  similar  in  construction  and  power  to  the  original 
model,  except  that  it  has  2  C  hoops,  1  D  hoop,  3  B  hoops,  and  3  A 
hoops. 


ARMAMENT  111 


12-INCH  BREECH-LOADING  RIFLE,  MODEL  OF  1892  (1896) 

This  rifle  was  originally  called  the  model  of  1892.  Its  breech 
mechanism  was  changed  to  a  design  similar  to  the  model  of  1895 — 
except  that  the  operating  crank  was  above  instead  of  below  the  tray. 
After  the  change  the  rifle  was  called  the  model  of  1896.  Only  one 
was  made. 


12-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1895 

This  rifle  is  similar  in  construction  and  power  to  the  model  of 
1888  Mn,  except  that  its  total  length  is  442.56  inches;  length  of  bore 
35  calibers  and  maximum  range  11,636  yards. 

The  breech  mechanism  (Stockett)  is  the  same  as  that  of  the  10-inch 
rifle  model  of  1895,  except  that  the  number  of  turns  of  the  operating 
crank  and  the  number  of  teeth  on  compound  gear  and  worm  wheel 
are  increased. 


12-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1895,  Mi 

This  rifle  is  practically  the  same  as  the  original  model. 

The  breech  mechanism  is  the  same  as  that  of  the  10-inch  rifle, 
model  of  1895,  except  in  dimensions,  and  that  the  number  of  turns  of 
the  operating  crank  and  the  number  of  teeth  on  the  compound  gear 
and  worm  wheel  are  increased. 


12-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1900 
(See  Plates  I,  II  and  III) 

This  rifle  is  exceedingly  powerful.  It  is  similar  in  construction  to 
the  model  of  1888,  except  as  follows: 

Stockett  breech  mechanism  is  provided  (for  description,  see  10-inch 
B.L.R.  Mod.  1895). 

Total  length  504.3  inches;  weight  59  tons;  length  of  bore  40 
calibers;  weight  of  propelling  charge,  nitro-cellulose  powder,  325 
pounds;  weight  of  igniter  charge  9  pounds;  weight  of  bursting  charge, 
gun  cotton,  for  A.P.  shot,  13  pounds;  for  A.P.  shell,  39.4  pounds. 

Originally  the  muzzle  velocity  of  this  model  was  2,550  foot-seconds, 
with  a  muzzle  energy  of  47,299  foot-tons.  With  this  velocity  it  is 
capable  of  penetrating  12  inches  of  latest  type  battleship  armor,  with 


112 


THE  SERVICE  OF  COAST  ARTILLERY 


normal  impact  of  8,700  yards;  11  inches  at  10,000  yards,  and  7  inches 
at  all  fighting  ranges.  In  developing  this  energy,  however,  the  high 
temperature  due  to  the  smokeless  powder  and  great  increase  in  volume 
of  gas,  produces  an  erosion  of  the  bore,  which  materially  shortens 
the  life  of  the  gun. 

This  fact  caused  the  reduction  of  the  service  muzzle  velocity  to 
2,250  foot-seconds,  which  has  normally  increased  the  life  of  the  gun 
from  4  to  5  years,  to  at  least  12  years,  in  peace  time. 

With  the  present  velocity  its  penetration  at  5,000  yards  is  13  inches. 
Maximum  pressure  38,000  pounds.  Maximum  elevation  permitted 
by  the  carriage  10  degrees;  maximum  range  at  this  elevation  13,513 
yards. 


FIG.  11.— Pit  of  12-inch  Mortars. 

12-lNCH  CAST-IRON  MORTAR,  MODEL  OF  1886 
(Cast-Iron  Body,  Steel  Hooped) 

This  mortar  is  constructed  of  cast  iron,  reinforced  by  two  rows  of 
short  steel  hoops;  that  is,  7  A  hoops,  breaking  joints  with  6  B  hoops. 
It  is  of  the  built-up  type,  the  method  of  construction  being  shown  in 
Fig.  2.  Mortars  have  110  breechplate;  the  breechblock  is  supported 
by  the  cast  iron  body  and  has  screwed  to  its  rear  face  a  face  plate, 
commonly  called,  the  "banjo,"  to  which  is  attached  the  block  handle 
or  handles. 

The  breech  mechanism  of  mortars  (see  Fig.  12  and  Plates  IV,  V  and 
VI)  is  practically  the  same  for  all  models,  except  those  of  the  wire- 


.. 


ARMAMENT 


113 


114  THE  SERVICE  OF  COAST  ARTILLERY 

wrapped  type  noted  at  the  beginning  of  this  chapter.  In  all  the  models 
described  herein  the  points  of  difference  are  of  a  minor  character.  In 
this  particular  model  the  threads  of  the  breechblock  have  the  ratchet 
section  instead  of  the  V  used  in  the  all-steel  mortars,  and  the  gear-rack 
teeth  are  cut  on  the  exterior  of  the  segment  instead  of  on  the  interior, 
as  in  the  later  models. 

The  breech  mechanism  of  mortars,  with  the  exceptions  noted 
above,  consists  of  the  breechblock,  obturator  spindle,  tray,  hinger 
face  plate,  rack,  translating  roller,  tray  latch,  securing  latch  or  tray 
back  latch,  firing  mechanism  of  safety-bar  slide,  and  associate  parts. 

The  breechblock  is  threaded  with  a  V  thread  with  rounded  top. 
The  rear  portion  is  left  unthreaded  to  prevent  the  entrance  of  dust. 
The  threaded  portion  is  divided  into  six  equal  sectors,  three  threaded 
and  three  slotted.  The  guide  grooves  fit  upon  and  pass  over  the 
rails  of  the  tray  when  the  breechblock  is  drawn  to  the  rear.  The  face 
plate  (or  " banjo"),  is  attached  to  the  breechblock  by  five  screws 
and  a  dovetail  tenon  fitting  in  a  transversely  slotted  seat.  The  arm 
has  a  rectangular  mortise  cut  perpendicularly  to  the  axis  of  the  breech- 
block, through  the  upper  end,  in  which  the  rotating  pinion  and  rotating 
crank  gear  are  housed.  ^ 

The  rotating  crank  gear  (the  lower  one  when  the  arm  of  the  face 
plate  is  pointing  upward)  is  mounted  upon  an  axle  which  extends  to 
the  rear  and  has  the  rotating  crank  mounted  upon  it.  This  rotating 
crank  gear  meshes  into  a  larger  one  above  it,  the  rotating  pinion, 
which  is  mounted  upon  a  second  axle  also  having  its  bearings  in  the 
walls  of  the  mortise.  The  bearings  are  bushed  with  bronze.  The 
rotating  gear  is  mounted  on  the  latter  journal,  in  front  of  the  arm. 
This  rotating  gear  meshes  into  a  circular  rack,  geared  on  the  interior, 
and  bolted  upon  the  rear  face  of  the  breech  in  a  recess  cut  for  the 
purpose.  This  rack  is  now  cut  in  the  solid  metal  of  rear  face  of  the 
A3  hoop.  The  rear  face  and  upper  surface  of  the  rack  are  flush  with 
the  face  of  the  breech  and  upper  surface  of  the  mortar. 

Rotating  the  rotating  crank  turns  the  rotating  crank  gear,  which 
turns  the  rotating  pinion  and  the  rotating  gear,  which,  being  engaged 
in  the  rack,  travels  in  it  and  causes  the  breechblock  to  rotate.  The 
rotating  crank  has  a  lock  consisting  of  a  housing,  two  studs,  a  spring 
and  a  handle.  The  housing  is  screwed  into  the  rear  side  of  the  face- 
plate arm.  The  front  stud  is  mounted  in  a  cylindrical  recess  in  the 
housing  and  extends  through  the  face-plate  arm.  It  moves  in  a 
groove  of  varying  depth  in  the  breech  of  the  gun.  A  rear  stud  enters 
the  rotating-crank  arm  from  the  front,  extends  to  the  rear,  and  has  a. 


*   THE          • 

{  UNIVERSITY 

OF 


ARMAMENT  1 15 

handle  screwed  upon  the  extension.  About  its  shank  is  a  spiral  spring 
with  its  front  bearing  against  the  rear  of  the  rear  stud  head.  The 
front  face  of  the  rear  stud  is  crowned,  enabling  the  crank  to  pass  the 
housing  by  compressing  the  spring.  As  long  as  the  front  stud  moves 
in  the  shallow  portion  of  its  groove  in  the  breech  it  entirely  fills  the 
recess  in  the  housing. 

When  the  rotation  of  the  breechblock  is  completed  and  the  front 
stud  arrives  at  the  well  at  the  end  of  the  groove,  thus  being  free  to 
move  forward,  the  pressure  of  the  spring  forces  the  rear  stud  into 
the  recess  in  the  housing,  latching  the  rotating  crank.  It  follows 
that  the  rotating  crank  is  also  latched  at  any  time  that  the  breech- 
block is  not  fully  translated  home.  In  the  earlier  models  there  is  no 
handle,  and  only  one  stud,  which  is  crowned  and  fits  into  a  seat  on  the 
front  face  of  the  rotating-crank  arm,  latching  the  rotating  crank. 
As  in  the  later  model,  the  rotating  crank  is  enabled  to  pass  the  housing 
by  compressing  the  spring.  A  handle  of  steel  or  bronze  is  attached 
to  the  face  plate. 

Obturator  Spindle 

The  obturator  spindle,  tray,  and  translating  roller  are  similar  to 
those  used  in  the  8-inch,  10-inch,  and  12-inch  rifles,  Model  of  1888.  A 
hinge  set  into  the  face  of  the  breech  and  secured  by  four  screws  is 
provided  with  two  lugs  in  which  the  hinge  pin  is  mounted,  and  with 
two  cylindrical  bosses  which  fit  in  corresponding  cavities  in  the  face  of 
the  breech.  The  translating  stud  attached  to  the  rear  face  of  the 
breechblock  projects  vertically  from  the  face  of  the  block.  It  is 
shaped  like  the  sector  of  a  thread  in  a  nut.  Previous  to  1896  it  was 
made  cylindrical  in  form.  When  the  block  is  rotated  through  the 
arc  necessary  to  unlock  it,  the  translating  stud  revolves  into  the  groove 
in  the  translating  roller. 

The  obturator  spindle  consists  of  the  spindle  (head  and  stem), 
pad,  front  and  rear  split  rings,  small  split  ring,  filling-in  disk,  obturator 
nut,  and  the  obturator-spindle  washers.  The  vent  is  drilled  through 
the  spindle,  in  the  front  of  which  there  is  a  copper  bushing  plug  forced 
into  an  undercut  on  the  face  of  the  head.  Vents  are  now  drilled  to  a 
diameter  of  0.200  inch  thoughout  with  a  radius  of  0.025  inch  at  front 
end.  This  bushing  may  be  replaced  when  badly  eroded. 

The  front  and  rear  rings  are  of  steel,  split  diagonally  through 
one  side.  They  are  slightly  larger  than  the  conical  gas-check  seat, 
and  are  sprung  together  in  being  forced  into  this  seat.  The  small 
split  ring  is  of  similar  construction,  but  slightly  smaller  than  the 


116  THE  SERVICE  OF  COAST  ARTILLERY 

obturator-spindle  stem.  The  rear  filling-in  disk  acts  as  a  washer 
in  rear  of  the  pad.  A  shoulder  on  its  front  face  supports  the  interior 
edge  of  the  rear  split  ring,  and  a  fillet  on  the  rear  face  of  the  obturator- 
spindle  head  performs  the  same  office  for  the  front  split  ring.  The 
obturator  nut  is  screwed  on  the  rear  end  of  the  stem  with  a  left-hand 
thread;  it  draws  the  obturator-spindle  head,  gas-check  pad,  and 
split  rings  to  a  bearing  against  the  face  of  the  breechblock.  It  abuts 
against  the  obturator-spindle  washers  and  has  under  its  front  edge  a 
thin  steel  dust  cover.  This  obturator  nut  is  now  provided  with  a 
clamp  screw  to  clamp  it  on  obturator  spindle  to  prevent  its  rotation, 
thus  doing  away  with  the  old  locking  nut.  In  some  of  the  earlier 
models  the  obturator  nut  has  a  right-hand  thread. 

The  four  obturator-spindle  washers  are  alternately  bronze  and 
steel.  They  reduce  the  friction  between  the  obturator  nut  and  the 
rear  face  of  the  breechblock  recess  and  enable  the  breechblock  to  be 
rotated  independently  of  the  gas  check,  during  the  first  part  of  its 
movement  in  unlocking.  They  are  assembled  with  a  bronze  washer 
in  front  and  the  others  alternating  steel  and  bronze. 

The  translating  roller  is  seated  in  a  right-hand  thread  in  the  upper 
surface  of  the  body  of  the  tray.  It  has  two  independent  threads  cut 
in  opposite  directions  on  its  surface.  The  translating  stud  engages 
in  the  left-hand  thread.  The  translating  crank  is  mounted  on  the 
squared  end  of  the  translating  roller.  The  rotation  of  this  crank 
causes  the  roller  to  unscrew  in  its  right-hand  thread  and  travel  back 
in  the  tray,  drawing  the  breechblock  with  it.  It  also  causes  the  trans- 
lating stud  attached  to  the  breechblock  to  travel  as  a  nut  in  the  left- 
hand  thread.  Thus  a  double  motion  of  translation  is  given  to  the 
breechblock,  drawing  it  on  to  the  tray  by  fewer  revolutions  of  the 
crank  than  if  either  motion  were  used  singly. 

The  tray  latch  secures  the  tray  to  the  face  of  the  breech  while  the 
breechblock  is  entering  or  being  withdrawn  from  its  seat  in  the  breech 
recess.  It  is  mounted  in  a  longitudinal  slot  in  the  web  on  the  under 
side  of  the  tray,  on  a  tray-latch  pivot.  Its  front  end  terminates  in  a 
hook  lip,  which  engages  in  the  tray-latch  catch  when  the  tray  is  against 
the  face  of  the  breech.  On  its  rear  end  is  a  transverse  handle.  A 
tray-spring  bolt  mounted  in  the  tray  above  the  tray  latch  holds  it 
so  that  it  can  not  be  unlatched  so  long  as  the  tray-spring  bolt  is  covered 
by  the  translating  roller. 

When  the  latter  is  quickly  withdrawn  beyond  it,  the  relation 
between  the  excess  of  weight  in  front  of  the  tray-latch  journal  and  the 
tension  of  the  tray-spring  bolt  spring  is  such  that  the  jar  will  unlatch 


OF   THE 

ER 

OF 


AKMAMENT  117 

it.  The  tray-latch  catch  is  a  recess  cut  into  the  face  of  the  breech. 
When  the  tray  is  swung  around  so  as  to  fully  uncover  the  breech,  it  is 
held  by  the  tray-latch,  which  is  mounted  in  a  mortise  in  the  hinge  on  a 
tray-back-latch  bolt  passing  through  the  hinge.  This  tray-back  latch 
engages  a  tray-back-latch  catch  on  the  tray.  It  is  released  by  lifting 
the  tray-back-latch  handle  at  its  left  end. 

Action  of  Breech  Mechanism. — When  the  breechblock  is  in  the 
firing  position  the  threads  are  in  bearing  with  those  of  the  breech  recess; 
the  face  plate  is  inclined  60  degrees  to  the  right;  the  rotating  crank 
is  pointed  toward  the  vent  and  is  held  in  position  by  the  rotating- 
crank  lock;  the  tray  is  against  the  face  of  the  breech;  the  tray  latch 
is  engaged  in  its  catch;  the  translating  stud  is  60  degrees  to  the  left  of 
its  seat  in  the  translating  roller;  the  translating  crank  is  vertical  with 
the  crank  pointing  downward,  and  the  pad  and  split  rings  are  in  the 
gas-check  seat. 

To  Open  the  Breech. — Pull  out  the  rotating-crank  lock,  turn  the 
rotating  crank  three  turns  in  direction  indicated  by  the  arrow  marked 
"open"  on  the  face  plate.  The  threads  of  the  breechblock  are  now 
opposite  the  slotted  sectors  of  the  breech  recess,  the  face  plate  is 
vertical,  the  rotating  crank  points  downward,  and  the  translating 
stud  is  in  the  translat  ing-roller  thread.  Then  turn  the  translating- 
roller  crank  three  turns  in  a  direction  opposite  that  of  the  hands  of  a 
clock,  ending  with  a  quick  motion  to  bring  the  breechblock  to  its  final 
position  in  the  tray  with  a  jar  which  will  release  the  tray  latch.  Grasp 
the  tray  handle  and  swing  the  tray  about  the  hinge  pin  till  the  tray- 
back  latch  engages  in  its  catch.  The  breechblock  swings  around  145 
degrees  and  clears  the  breech  for  loading. 

To  Close  the  Breech. — Release  the  tray-back  latch  by  raising  its 
left  end;  swing  the  tray  against  the  face  of  the  breech  by  taking  hold 
of  the  tray  handle;  turn  the  translating  roller  three  turns  in  the  direc- 
tion of  the  hands  of  a  clock;  then  turn  the  rotating  crank  three  turns 
in  the  same  direction.  It  is  not  necessary  to  count  the  number  of 
turns  either  in  opening  or  closing  the  breech,  as  there  are  stops  for 
all  motions. 

To  Remove  and  Dismount  the  Breech  Mechanism. — Turn  the  rotating 
crank  until  the  translating  stud  is  out  of  its  seat  m  the  translating 
roller,  thus  bringing  the  face  plate  to  its  vertical  position,  remove  the 
translating  roller;  grasp  the  breechblock  handle  and  withdraw  the 
breechblock  on  to  the  tray  as  far  as  possible,  so  that  the  obturator 
spindle  head  will  clear  the  breech  recess;  raise  the  tray  latch  and 
swing  the  tray  around ;  remove  the  obturator-spindle  nut  and  washers, 


118  THE  SERVICE  OF  COAST  ARTILLERY 

then  take  off  the  breechblock  by  passing  a  rope  through  it  and  slinging 
it,  using  a  gin  or  crane. 

The  face  plate,  when  necessary,  can  then  be  removed  by  taking 
out  the  screws,  but  this  should  not  be  done  except  at  the  gun  factory. 

In  case  any  nuts  are  to  be  removed,  their  pins  should  be  driven 
out  carefully,  using  a  drift  so  as  not  to  batter  them. 

The  tray  is  removed  as  follows:  Remove  the  tray  latch,  block  up 
under  the  tray  or  sling  it  securely  and  remove  the  hinge  pin.  The 
tray -back  latch  is  removed  after  removing  the  tray. 

To  Assemble  the  Breech  Mechanism. — Put  on  tray-back  latch, 
then  the  tray,  then  the  tray  latch;  put  on  the  breechblock  on  the 
tray  (by  using  a  sling  as  before) ;  put  in  the  obturator  spindle,  then  the 
obturator  nut  and  washers,  swing  the  tray  around  against  the  face  of 
the  breech;  push  the  breechblock  home;  rotate  it  slightly  and  put  in 
the  translating  roller. 

The  above  order  of  assembling  assumes  that  the  face  plate  has 
not  been  removed  from  the  breechblock.  In  case  it  has,  it  should  be 
put  on  before  the  breechblock  is  put  on  the  tray. 

If,  after  firing,  the  breechblock  can  not  be  unlocked  by  the  rotating 
crank,  remove  the  obturator  nut  and  obturator-spindle  washers,  and 
then  unlock  the  breechblock,  leaving  the  spindle  in  the  gun.  Then 
remove  the  spindle  by  inserting  a  heavy  timber  in  the  muzzle  and 
striking  the  head  until  it  is  loosened,  being  careful  not  to  allow  the 
spindle  to  drop. 

The  bore  has  68  grooves;  twist  of  rifling,  one  turn  in  42  calibers 
to  one  turn  in  25  calibers. 

The  total  length  is  129  inches;  weight  14.25  tons;  length  of  bore 
9  calibers;  weight  of.  projectiles,  deck-piercing  shell,  capped,  1,046 
pounds  and  824  pounds.  With  1,046-pound  projectile  the  powder 
charges,  nitro-cellulose  powder,  are  issued  made  up,  to  give  velocities 
for  zones  as  follows:  First  zone  560  foot-seconds;  second  zone  610 
foot-seconds;  third  zone  670  foot-seconds;  fourth  zone  743  foot- 
seconds;  fifth  zone  837  foot-seconds;  sixth  zone  910  foot-seconds. 
With  824-pound  projectile,  seventh  zone  1,050  foot-seconds.  Weight 
of  propelling  charge  approximately  33  pounds;  weight  of  igniter 
charge  1.25  pounds. 

Muzzle  energy,  between  6,298  arid  6,544  foot-tons.  Maximum 
pressure  27,500  pounds  per  square  inch.  Maximum  range,  with  45 
degrees  elevation,  9,557  yards.  Minimum  range,  with  65  degrees 
elevation,  2,225  yards. 


THE 

UNIVERSITY 

OF 


ARMAMENT  119 

12-lNCH  CAST-IRON  MORTAR,  MODEL  OF  1886,  M 

This  mortar  is  similar  in  construction  and  power  to  the  original 
model,  except  that  it  has  5  A  hoops. 

12-lNCH  STEEL  MORTAR,  MODEL  OF  1886-90,  Mi 

This  mortar  is  similar  in  construction  and  power  to  the  model  of 
1890,  except  that  it  has  5  A  hoops  breaking  joints  with  5  B  hoops. 

Total  length  129.25  inches;  weight  12  tons;  twist  of  rifling,  one 
turn  in  40  calibers  to  one  turn  in  25  calibers.  Only  a  few  of  this  model 
were  made. 

12-lNCH  STEEL  MORTAR,  MODEL  OF  1890 

This  mortar  is  similar  in  construction  to  the  model  of  1886,  except 
that  it  has  a  tube,  jacket,  breech  bushing,  2  C  hoops,  1  D  hoop,  3  A 
hoops  and  other  parts  as  shown  in  Fig.  3. 

The  breechblock  is  supported  by  the  jacket  through  the  breech 
bushing.  The  two  C  hoops  are  shrunk  on  the  tube  from  the  front, 
each  having  a  shoulder  abutting  against  one  on  the  tube.  Four 
securing  pins,  screwed  through  the  C2  hoop  into  the  tube  prevent 
the  C  hoops  from  moving  to  the  front.  The  D  hoop  is  put  on  from 
the  front  and  abuts  against  the  shoulder  on  the  jacket,  covering  the 
joint  between  it  and  the  Cl  hoop.  The  Al  hoop,  assembled  from  the 
rear,  abuts  against  a  shoulder  on  the  D  hoop  and  covers  the  joint 
between  the  jacket  and  the  D  hoop.  The  A2  hoop,  or  trunnion  hoop, 
abuts  against  a  shoulder  on  the  jacket. 

The  bore  has  72  grooves;  twist  of  rifling  one  turn  in  40  calibers  to 
one  turn  in  20  calibers. 

The  total  length  is  141.125  inches;  weight  13  tons;  length  of 
bore  10  calibers.  The  powder  charges,  nitro-cellulose  powder,  weigh 
from  54  to  62  pounds;  igniter  charge  1.25  pounds.  With  1,046  pound 
projectile  the  powder  charges  are  issued  made  up,  to  give  velocities 
for  zones  as  follows:  First  zone  550  foot-seconds;  second  zone  600 
foot-seconds;  third  zone  660  foot-seconds;  fourth  zone  725  foot-seconds; 
fifth  zone  810  foot-seconds;  sixth  zone  915  foot-seconds;  seventh  zone 
1,050  foot-seconds.  With  824-pound  projectile,  eighth  zone  1,300  foot- 
seconds. 

Muzzle  energy  between  9,647  and  10,077  foot-tons.  Maximum 
pressure  33,000  pounds  per  square  inch.  Maximum  range,  with  45 
degrees  elevation,  12,019  yards.  Minimum  range,  with  65  degrees 
elevation,  2,210  yards. 


120  THE  SERVICE  OF  COAST  ARTILLERY 

12-INCH  STEEL  MORTAR,  MODEL  OF  1890,  Mi 
(See  Plates  IV,  V  and  VI) 

This  is  the  latest  type  of  built-up  forged  steel  mortar.  It  is 
practically  identical  with  the  original  model. 

10-lNCH  STEEL  MORTAR,  MODEL  OF  1890 

This  mortar  is  similar  in  construction  to  the  12-inch  model  of  1890. 

Total  length  117.1  inches;  weight  7.5  tons;  length  of  bore  10 
calibers. 

Weight  of  projectile  604  pounds;  weight  of  charge,  including 
igniter,  604  pounds. 

Muzzle  velocity  1,150  foot-seconds.  Muzzle  energy  5,287  foot- 
tons.  Maximum  pressure  33,000  pounds  per  square  inch.  Maximum 
range  10,798  yards.  This  type  was  entirely  experimental  and  very 
few  were  made. 

10-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1888 
(See  Plates  VII  and  VIII) 

This  rifle  is  similar  in  construction  to  rifles  previously  described. 
It  has  7  C  hoops,  5  A  hoops,  2  D  hoops,  and  4  B  hoops. 

Weight  30  tons;  total  length  30.6  feet;  length  of  bore  34  calibers; 
the  bore  has  60  grooves;  twist  of  rifling,  one  turn  in  50  calibers  to  one 
turn  in  20  calibers. 

The  breech  mechanism,  commonly  called  the  "  interrupted  screw 
system,"  consists  of  the  breechblock,  obturator,  breechplate,  rotating 
crank  and  gears,  tray,  translating  roller,  translating  crank,  tray  latch, 
tray  back  latch,  hinge  pin,  and  associate  parts  as  shown  in  Plates 
VII  and  VIII,  and  Fig.  4.  The  principal  parts  of  the  breechblock 
are  the  threaded  sectors,  the  slotted  sectors,  the  guide  grooves,  and 
the  translating  stud. 

The  block  is  threaded  with  a  V  thread  with  rounded  top.  The 
rear  portion  is  left  unthreaded  to  prevent  the  entrance  of  dust.  The 
threaded  portion  is  divided  into  eight  equal  sectors,  four  threaded  and 
four  slotted.  The  two  guide  grooves  are  cut  in  the  two  bottom  slotted 
sectors  30  degrees  each  side  of  the  lowest  element  of  the  unlocked 
breechblock.  They  fit  upon  and  pass  over  the  rails  of  the  tray  when 
the  breechblock  is  drawn  to  the  rear. 

The  breechblock  is  slotted  across  its  breech  face  for  a  rotating  lever 


ARMAMENT  121 

which  may  be  attached  by  two  screw  bolts.  The  translating  stud 
projects  radially  from  the  rear  face  of  the  block  and  is  secured  in  its 
seat  by  a  screw. 

When  the  breechblock  is  rotated  the  ^cessary  to  unlock 

it,  the  stud  revolves  into  the  groove  i  ng  roller.  The 

obturator  consists  of  the  spindle,  pad,  tl  .,  and  small  split 

rings,  the  filling-in  disc,  the  obturator  ma  aie  obturator-spindle 

washers.  The  vent  is  drilled  through  the  swindle,  in  the  front  of  which 
is  a  copper  bushing  forced  into  an  undercut  in  the  face  of  the  mushroom 
head.  This  bushing  permits  of  being  replaced  when  badly  eroded. 
In  passing  through  this  plug,  the  vent  contracts  from  two-tenths  to 
one-tenth  of  an  inch.  The  rear  end  of  the  vent  channel  is  enlarged  and 
threaded  for  an  obturating  primer  used  to  ignite  the  charge. 

The  pad  is  made  of  asbestos  and  tallow  with  a  canvas  covering. 
The  front  and  rear  split  rings  are  of  steel,  split  diagonally  through 
one  side.  They  are  slightly  larger  than  the  conical  seat,  and  are 
sprung  together  in  being  forced  into  place.  The  small  split  ring  is  of 
similar  construction,  and  fits  tightly  over  the  spindle.  The  filling-in 
(or  gas-check)  disc  acts  as  a  washer  in  rear  of  the  pad;  a  shoulder  on 
its  front  face  supports  the  interior  edge  of  the  rear  split  ring;  a  fillet 
on  the  rear  face  of  the  obturator-spindle  head  performs  the  same  office 
for  the  front  split  ring.  The  obturator  nut  is  screwed  on  the  rear  end 
of  the  spindle  with  a  right-hand  thread  in  the  earlier  guns,  and  in  the 
later  with  a  left-hand  thread;  it  abuts  against  the  spindle  washers, 
draws  the  obturator  spindle  head  and  pad  to  a  bearing  against  the 
face  of  the  block,  and  has  under  its  front  edge  a  thin  steel-spring  washer, 
designed  to  form  a  tight  joint  over  the  recess  for  the  spindle  washers 
to  prevent  the  entrance  of  dust,  sand,  etc.  It  is  provided  with  a  clamp 
screw  to  prevent  the  obturator  nut  from  unscrewing. 

The  four  obturator  spindle  washers  are  alternately  bronze  and 
steel,  assembled  with  one  of  the  former  in  front.  They  reduce  the 
friction  between  the  spindle  nut  and  the  rear  face  of  the  block  recess, 
enabling  the  block  to  be  rotated  independently  of  the  pad,  leaving  the 
latter  in  its  seat  until  the  block  is  unlocked. 

The  breech  plate  is  a  steel  casting  attached  to  the  breech  face  by 
two  large  screw  bolts.  On  it  are  mounted  the  rotating  mechanism, 
securing  latch,  and  the  hinge  lugs.  A  recess  in.  its  face  acts  as  a  catch 
for  the  tray  latch.  The  rotating  mechanism  for  the  block  consists  of 
the  rotating  ring,  the  bronze  bushing,  the  rotating  gears,  and  the 
rotating  crank  and  associate  parts.  The  steel  rotating  ring  encircles 
the  breechblock  and  is  mounted  in  the  bronze  bushing.  From  this 


122  THE  SERVICE  OF  COAST  ARTILLERY 

ring  projects  radially  the  gear  segment  of  70  degrees,  in  which  the  teeth 
are  cut.  The  gear  ring  fits  over  the  cylindrical  portion  of  the  block, 
with  a  lug  extending  into  the  upper  right-hand  slotted  sector,  which 
is  prolonged  to  the  rear  to  receive  it  when  the  block  is  locked.  This 
lug  acts  as  a  key  in  the  sector  to  constrain  the  block  to  rotate,  and 
when  the  latter  is  withdrawn  from  the  screw  box  the  slotted  sector 
slides  from  under  the  lug. 

The  bronze  bushing  is  attached  to  the  breech  plate  by  four  screw 
bolts  and  is  lubricated  by  oil  channels  in  its  face. 

The  rotating  gears  are  three  in  number — two  single  and  one  com- 
pound; the  first,  single,  called  the  rotating-crank  pinion,  is  solid  with 
its  journal,  which  works  in  bronze  bushings  and  extends  through  the 
breech  plate,  the  rotating  crank  being  mounted  on  the  rear  end  and 
secured  thereon  by  a  nut  and  pin.  The  intermediate  gear,  also  single, 
works  into  the  larger  wheel  of  the  compound  gear.  The  latter  is  in  one 
piece,  forming  two  gears  of  different  diameters;  the  smaller  engages 
the  gear  segment,  and  thus,  by  the  crank,  the  breechblock  is  rotated. 

There  is  a  spring  catch  called  the  rotating-crank  box,  mounted  on 
the  rear  face  of  the  rotating  crank,  by  which  the  gear  system  is  locked 
when  the  breech  is  closed  and  the  block  rotated  to  its  locked  position. 
This  lock  consists  of  two  locking  bolts,  each  controlled  by  a  spiral 
spring  which  hold  the  bolts  down  in  the  locking  recess  in  the  breech 
face  of  the  gun.  These  locking  bolts  act  alternately,  that  is,  one  locks 
the  rotating  crank  when  the  breech  is  closed  and  ready  for  firing,  and 
the  other  locks  the  rotating  crank  in  its  horizontal  position  when  the 
breech  is  open  and  ready  for  loading.  These  bolts  are  manipulated 
by  means  of  a  small  crank  which  is  provided  with  inclined  or  beveled 
surfaces  at  its  pivoted  end.  These  surfaces  come  into  contact  with 
lugs  formed  on  the  outer  end  of  the  locking  bolts,  and  by  swinging  the 
small  crank  to  the  right  the  breech  can  be  opened,  and  to  the  left  the 
breech  can  be  locked.  The  handle  of  the  rotating  crank  is  covered 
with  a  loose  sleeve. 

By  the  rotation  of  the  block  the  translating  stud  is  revolved  into 
the  thread  of  the  translating  roller,  and  the  block  is  in  position  to  be 
drawn  directly  to  the  rear  out  of  the  breech  recess  on  to  the  tray. 
The  tray,  of  bronze,  is  mounted  in  rear  of  the  breech,  supported  on  the 
right-hand  side  by  a  huge  pin  working  in  lugs  on  the  breech  plate. 
The  associate  parts  are  the  translating  roller  and  crank,  the  tray  latch, 
and  the  catch  for  the  securing  latch. 

The  translating  roller  is  seated  in  a  right-hand  thread  in  the  upper 
portion  of  the  tray  and  has  also  cut  upon  it  a  left-hand  thread  in 


ARMAMENT  123 

which  the  translating  stud  works.  The  action  of  the  crank  causes 
the  roller  to  unscrew  in  its  right-hand  thread  and  the  translating  stud 
attached  to  the  block  to  travel  as  a  nut  in  the  left-hand  thread,  drawing 
the  block  with  it;  thus  the  translation  of  the  block  is  given  by  fewer 
revolutions  of  the  crank  than  if  either  were  used  singly,  and  has  only  to 
travel  one-half  the  distance. 

The  tray  latch  secures  the  tray  to  the  face  of  the  breech;  it  is 
pivoted  in  a  longitudinal  slot  on  the  under  side  of  the  tray,  has  the 
front  end  terminating  in  a  hook  lip,  which  engages  in  its  seat  in  the 
breech  plate,  and  has  a  transverse  handle  on  its  rear  end.  A  spring 
bolt,  mounted  in  the  tray,  holds  the  latch  so  that  it  can  not  be  released 
while  its  bolt  is  covered  by  the  translating  roller.  When  the  latter 
is  quickly  withdrawn  beyond  the  bolt,  the  relation  between  the  excess 
of  weight  in  front  of  the  latch  journal  and  the  tension  of  the  tray- 
spring  bolt  is  such  that  the  jar  will  unlatch  the  tray.  Just  in  rear 
of  the  latch  spring  is  a  bolt,  passing  through  the  web  of  the  tray  and 
into  a  recess  in  the  roller  when  the  block  is  withdrawn,  thus  preventing 
any  motion  of  the  block  to  the  front  when  in  the  loading  position. 

This  bolt  is  operated  by  a  lever  hinged  to  the  web  of  the  tray,  one 
end  entering  the  slot  in  the  bolt,  the  other  joined  by  a  link,  which, 
in  its  turn,  is  joined  to  the  tray  latch.  When  the  latch  is  unfastened  its 
rear  end  is  forced  downward  by  the  spring  bolt,  thus,  through  the 
connections,  raising  the  lock  bolt"  into  its  seat  in  the  roller;  when 
the  latch  is  fastened  the  lock  bolt  moves  downward  out  of  its  seat. 

The  tray  latch  being  unfastened,  the  tray  may  be  swung  to  the 
right  until  caught  by  the  securing  latch.  This  latch  is  mounted  in  a 
recess  in  the  breech  plate,  through  which  its  handle  protrudes  on  the 
left  and  its  catch  end  on  the  right;  its  pivot  is  a  short  screw,  with 
countersunk  head  located  in  the  breech  plate  directly  back  of  the 
tray  hinge.  The  latch  engages  in  a  catch  on  the  diagonal  web  of  the 
tray,  arid  may  be  released  by  lifting  the  handle  or  pressing  down  the 
latch  end. 

The  hinge  pin  is  a  cylindrical  bar,  mounted  in  two  lugs  on  the 
right  side  of  the  breech  plate;  it  is  entered  from  below  and  held  in 
position  by  two  small  screws  through  the  tray  hinge,  thus  locking 
hinge  and  pin  together.  An  oil  hole  in  the  upper  hinge  lug  permits 
of  the  pin  being  lubricated. 

Action  of  Breech  Mechanism. — When  the  breechblock  is  in  the 
firing  position  the  threads  are  in  bearing  with  those  in  the  breech 
recess;  the  rotating  crank  is  vertical;  the  rotating-crank  lock  bolt  is 
bearing  in  its  recess.  The  translating  stud  is  45  degrees  to  the  left 


124  THE  SERVICE  OF  COAST  ARTILLERY 

of  its  seat  in  the  translating  roller;  the  tray  latch  is  engaged  in  its 
catch;  the  rotating  ring  is  rotated  to  extreme  right-hand  position 
and  the  gas-check  pad  is  in  its  seat. 

To  Open  the  Breech. — Turn  the  winged  nut  of  the  rotating  crank 
catch  (lock)  180  degrees  to  the  left;  turn  the  rotating  crank  in  the 
direction  of  the  hands  of  a  clock,  as  indicated  by  the  arrow  marked 
"open"  on  the  breech  plate,  until  the  translating  stud  is  in  the  trans- 
lating-roller  thread ;  the  rotating  crank  latch  (lock)  will  then  be  opposite 
the  upper  steel  lock  plate,  which  has  a  recess  in  its  center  to  receive  it; 
the  guide  grooves  in  the  breechblock  will  be  opposite  the  guide  rails  in 
the  tray.  Turn  the  translating  crank  in  a  contraclockwise  direction 
four  times,  ending  with  a  quick  motion  to  bring  the  block  into  its 
final  position  in  the  tray  with  a  jar,  which  will  release  the  tray  latch 
and  swing  the  tray  until  the  securing  latch  engages  the  catch. 

To  Close  the  Breech. — Release  the  securing  latch;  swing  the  tray 
to  the  face  of  the  breech;  reverse  the  motion  of  the  translating  crank 
until  the  breechblock  is  seated,  then  that  of  the  winged  nut  of  the 
rotating-crank  catch  (lock),  and  that  of  the  rotating  crank. 

To  Remove  and  Dismantle  the  Breech  Mechanism. — The  operations 
are  the  reverse  of  those  described  for  assembling  it.  If,  after  firing, 
the  block  can  not  be  unlocked  by  the  rotating  crank,  put  on  the 
rotating  lever  and  endeavor  to  turn  the  block.  If  this  fail,  remove 
the  obturator  nuts  and  washers  and  unscrew  the  block,  leaving  the 
obturator  in  the  gun.  If  the  block  can  not  be  unscrewed,  remove 
the  tray  and  breech  plate.  Support  the  tray  by  blocking  and  take  out 
the  hinge-pin  bolt  and  remove  the  hinge  pin  and  tray.  Then  support  the 
breech  plate  by  blocking  and  turn  out  the  breech-plate  screws,  loosen- 
ing all  before  any  are  entirely  removed,  and  taking  out  the  top  and  side 
ones  last.  To  avoid  marring  the  thread,  let  one  man  hold  a  heavy 
screw-driver  in  the  slot  and  a  second  turn  its  blade  with  a  screw 
wrench,  catching  the  blade  near  the  screw  head.  Put  on  the  rotating 
lever  and  unscrew  the  block.  The  breech  plate  should  not  be  taken 
off  unless  it  be  absolutely  necessary;  if  necessary  to  remove  it,  an 
eyebolt,  which  screws  into  the  oil  hole,  is  provided  for  convenience 
in  handling.  If  the  block  can  be  unlocked,  but  not  drawn  back,  aid 
the  translating  roller  by  gently  ramming  on  the  face  of  the  obturator, 
interposing  a  hard-wood  block  between  the  rammer  and  the  obturator. 

To  Assemble  Breech  Mechanism. — The  tray  will  be  swung  in  the 
loading  position,  in  which  it  is  held  by  the  tray-back  latch.  The 
translating  roller  must  be  removed  if  it  should  have  been  put  into  the 
tray  previously,  but  this  should  not  have  been  done.  The  obturating 


f 


OF    THE 

UNIVERSITY 

OF 


ARMAMENT  125 

spindle  with  the  gas-check  pad  will  be  removed  from  the  breechblock, 
a  rope  sling  will  be  passed  over  the  threads  around  the  center  of  the 
breechblock  and  at  right  angles  to  its  axis,  the  block  being  in  trans- 
lating position — i.  e.,  the  translating  stud  at  its  rear  end  points  down- 
ward. The  sling  will  be  attached  to  the  hook  of  the  loading  crane  or 
the  gin.  The  breechblock  will  be  hoisted  until  it  can  be  swung 
into  the  screw  chamber;  it  will  be  inserted  as  far  as  the  rope  per- 
mits. A  handspike  will  be  inserted  into  the  spindle  cavity,  and  by 
means  of  this  two  or  three  men  can  hold  the  block  in  place  while  the 
position  of  the  rope  sling  is  being  changed  farther  back.  The  block 
will  now  be  forced  into  the  breech  recess  and  rotated  till  the  rotating 
crank  reaches  its  vertical  terminal  position. 

The  tray  will  now  be  swung  to  the  breech  plate  ancT  the  translating 
roller  screwed  into  the  tray  for  the  first  time.  The  translating  roller 
should  not  be  screwed  home  with  the  tray  in  any  other  than  the  firing 
position,  otherwise  the  rear  end  of  the  tray  latch  would  have  to  be 
lifted  up  to  the  proper  height  to  prevent  interference  between  the 
lock  bolts  and  the  translating  roller. 

In  case  neither  loading  crane  nor  gin  are  available,  the  shot  truck 
may  be  utilized.  The  breechblock  is  rolled  onto  the  truck  by  means 
of  a  plank  ramp,  and  supported  thereon  in  its  proper  position  by 
means  of  bits  of  wood.  The  shot  truck  will  then  be  adjusted  to  the 
proper  height  and  angle  and  the  breechblock  forced  into  the  breech 
recess  and  rotated,  as  above  described. 

The  operation  of  inserting  and  adjusting  the  obturating  spindle  is 
as  follows :  The  breech  will  be  opened  and  breechblock  and  tray  swung 
into  the  loading  position.  The  obturator  spindle,  with  the  split  rings 
and  pad  in  place,  will  be  inserted  into  the  breechblock  and  will  be 
secured  by  screwing  up  the  obturator  nut  on  the  rear  end  of  the  spindle. 
The  breechblock  is  then  translated  and  rotated  into  the  firing  position 
and  the  wrench  applied  to  the  large  nut,  which  is  tightened  as  much  as 
possible  by  one  man.  The  clamping  screw  on  the  obturator  nut  should 
then  be  tightened.  This  screw  should  be  set  up  only  moderately  hard. 
The  spindle  is  properly  adjusted  if  while  it  has  no  play  longitudinally, 
it  can  be  turned  round  freely  by  taking  hold  of  the  obturator-spindle 
(mushroom)  head  with  both  hands. 

This  last  adjustment  may  have  to  be  repeated  after  a  few  rounds 
have  been  fired,  if  it  is  found  that  the  spindle  has  any  longitudinal 
play. 

Weight  of  projectile,  capped,  604  pounds;  weight  of  propelling 
charge,  nitro-celullose  powder,  155  pounds;  weight  of  igniter  charge, 


126  THE  SERVICE  OF  COAST  ARTILLERY 

4  pounds;    weight  of  bursting  charge,  gun  cotton,  22.4  pounds,  for 
A.P.  shell;   7.5  pounds  for  A.P.  shot. 

Muzzle  velocity  2,250  foot-seconds.  Maximum  pressure,  38,000 
pounds  per  square  inch.  Muzzle  energy,  21,293  foot-tons.  Maximum 
range  12,259  yards.  Penetration  in  Krupp  cemented  armor  at  5,000 
yards  9.8  inches. 

10-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1888  Mi 

This  rifle  is  similar  in  construction  and  power  to  the  Model  of  1888, 
and  differs  only  in  having  5  C  hoops. 

10-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1888  Mil 

This  rifle  is  similar  in  construction  and  power  to  the  Model  of  1888, 
and  differs  only  in  the  following  points: 

2  C  hoops,  1  D  hoop,  3  A  hoops,  and  3  B  hoops. 

The  steel  breech  plate  and  bronze  bushing  used  in  the  other  models 
are  replaced  in  this  one  by  a  bronze  plate. 

10-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1895 

This  rifle  is  similar  in  construction  and  power  to  the  Model  of  1888, 
and  differs  only  in  the  following  points: 

Total  length  369.1  inches;  weight  30  tons;  length  of  bore,  35 
calibers. 

The  breech  mechanism,  known  as  the  Stockett  system  (see  Fig. 
13  and  Plates  IX  and  X),  consists  of  the  breechblock,  block-locking 
device,  obturator,  tray,  tray  latch,  hinge,  compound  gear  worm-wheel, 
worm  and  shaft,  hinge  pin  and  nut,  rotating  crank,  ball  bearings  and 
bronze  bushings  for  worm  shaft. 

The  breechblock  has  6  threaded  and  6  slotted  sectors.  From  the 
rear  face,  to  the  right,  projects  a  rotating  lug  with  teeth,  into  which 
mesh  the  teeth  of  the  compound  gear.  Projections  on  the  upper  and 
lower  edges  of  this  lug  strike  against  the  gear  and  limit  the  rotation 
of  the  block  in  both  directions.  A  translating  rack  is  cut  in  the  slotted 
sector  which  is  at  the  same  height  as  the  compound  gear  when  the 
block  has  been  fully  rotated  for  withdrawing.  The  function  of  this 
rack  in  conjunction  with  the  compound  gear,  is  to  withdraw  the 
breechblock,  swing  it  and  the  tray  into  the  loading  position,  and  in 
closing  the  breech  to  perform  the  reverse  operation.  The  breech- 
block has  two  guide  grooves  each  30  degrees  from  the  lowest  element  of 


ARMAMENT 


127 


the  block,  when  it  is  in  position  for  withdrawing,  and  ending  in  shoulders 
near  the  front  face. 

There  are  two  short  grooves,  midway  between  the  guide  grooves 
and  parallel  to  them  at  opposite  ends  of  the  block,  ending  in  inclined 
shoulders;  they  form  seats  for  the  toes  of  the  tray  latch  when  the 
block  is  withdrawn. 

The  block-locking  device  consists  of  a  bell-crank  lever  pivoted 
to  the  breech  face  near  the  upper  end  oLthe  hinge  pin,  the  longer  arm 
of  which  is  connected  to  a  spring-controlled  locking  bolt,  which  is 


ft  Thrust  Bearings 

Shaft  Bu  shiny. 
Worm  Shaft 


FIG.  13. 

seated  in  the  breech  face,  its  lower  end  being  engaged  in  a  notch  cut 
into  the  periphery  of  the  block.  The  short  arm  of  the  bell  crank  is 
arranged  to  fit  into  a  notch  cut  into  a  cap  fitted  to  the  upper  end  of 
the  hinge  pin.  The  bell  crank  is  provided  with  an  operating  handle 
for  controlling  the  locking  bolt.  The  block-locking  bolt  must  be 
tripped  from  its  seat  in  the  breechblock  before  the  breech  mechanism 
can  be  opened,  that  is,  before  the  breechblock  can  be  rotated.  During 
the  rotation  and  translation  of  the  block  the  short  arm  of  the  bell- 
crank  lever  is  out  of  its  notch  in  the  hinge-pin  cap  and  is  bearing  against 


128  THE  SERVICE  OF  COAST  ARTILLERY 

the  periphery  of  the  cap;  this  holds  or  supports  the  locking  bolt  in 
its  upward  or  unlocked  position,  so  that  there  is  no  interference  between 
the  locking  bolt  and  the  breechblock  when  the  latter  is  being  closed. 
The  locking  bolt  works  automatically  when  the  breech  mechanism  is 
closed,  but  must  be  operated  by  hand  before  the  breechblock  can  be 
rotated  for  opening. 

The  obturator  is  of  the  same  construction  as  for  the  model  1888 
gun,  except  that  ball  bearings  are  used  instead  of  spindle  washers. 
The  tray  is  of  steel,  mounted  in  rear  of  the  breech,  and  consists  of 
two  guide  rails,  a  cylindrical  hinge,  and  a  heavy  connecting  web.  A 
hinge  pin  passing  through  two  lugs  on  the  hinge  plate  supports  the 
tray.  A  tray  latch,  with  locking  bolt  and  spring,  is  also  provided. 
The  tray  latch  consists  of  the  latch  proper,  and  its  catch,  with  latch 
spring,  locking  bolt  and  spring,  and  the  operating  stud. 

The  latch  proper  is  a  steel  lever,  pivoted  by  a  bolt  to  the  web  of 
the  tray.  It  has  a  toe  and  handle  at  the  rear  end,  and  a  toe  and  hook 
at  the  front  end.  The  front  toe  is  bored  through  for  the  passage  of 
the  operating  stud,  and  there  is  a  seat  on  the  upper  surface  of  the 
latch  for  the  latch  spring.  The  latch  spring  is  spiral,  and  is  seated  in 
the  lower  face  of  the  web  and  the  upper  space  of  the  front  half  of  the 
latch.  The  locking  bolt  is  cylindrical,  and  has  a  spiral  spring  in  rear, 
constantly  pushing  it  forward.  The  operating  stud,  which  controls 
the  locking  bolt,  passes  through  the  front  toe  of  the  latch.  The  tray- 
latch  catch  is  a  steel  stud,  screwed  into  the  breech,  and  is  of  a  shape  to 
receive  the  hook  of  the  latch.  The  hinge  plate  is  of  steel,  and  is 
assembled  by  seven  screw  bolts  to  the  breech  of  the  gun,  on  the  right- 
hand  side.  Its  rear  face  is  flush  with  the  breech,  and  has  two  lugs 
for  the  hinge  pin.  The  lower  end  of  the  plate  is  bored  out  to  receive 
the  worm  and  shaft,  and  its  bearings. 

The  hinge  pin  is  cylindrical,  with  a  flange  on  top,  a  square  surface 
for  the  bronze  worm-wheel  beneath  the  lower  lug,  and  a  thread  for  a 
securing  nut  below  the  wheel.  Just  below  the  upper  lug,  at  opposite 
extremities  of  a  diameter,  are  two  splines,  upon  which  the  compound 
gear  is  assembled.  The  upper  lug  hole  is  large  enough  to  permit 
these  splines  passing  through,  and  the  pin  is  correspondingly  enlarged 
at  the  upper  end.  The  compound  gear  is  assembled  between  the  upper 
hinge  lug  and  the  hinge,  and  is  secured  from  rotating  on  the  pin  by  the 
splines  that  fit  into  two  grooves  on  the  inner  surface  of  the  gear.  The 
latter  is  formed  by  first  cutting  large  tooth-shaped  screw  threads, 
and  then  cutting  longitudinal  grooves  at  regular  intervals,  thus  forming 
a  combined  spiral  gear  (to  rotate  the  block),  and  a  pinion  (to  operate 


ARMAMENT  129 

on  the  translating  rack).  A  ball-bearing  washer  of  steel  is  placed 
between  the  hinge  and  lower  hinge  lock,  to  reduce  friction  in  swinging 
the  tray  and  block.  Between  the  ends  of  the  worm  and  bronze 
bushing  are  placed  hardened  steel  ball  bearings,  to  reduce  the  friction 
clue  to  the  end  thrust.  The  outer  end  of  the  shaft  is  squared  to  receive 
the  crank,  the  handle  of  which  has  a  loose-fitting  brass  sleeve  to 
facilitate  operation. 

Action  of  the  Breech  Mechanism. — The  block,  when  in  firing  position, 
has  its  threads  engaged  in  those  of  the  breech  recess,  and  is  provided 
with  a  locking  bolt  fitted  in  a  recess  in  the  breech  face  of  the  gun, 
having  its  lower  end  seated  in  a  notch  formed  on  the  periphery  of  the 
block.  The  upper  teeth  of  the  rotating  rack  are  engaged  in  those  of 
the  compound  gear;  the  tray  is  latched  to  the  breech;  the  rear  toe 
of  the  latch  projects  above  the  upper  surface  of  the  tray;  the  front 
toe  is  on  a  level  with  this  surface,  and  the  rear  face  of  this  toe  retains 
the  latch  locking  bolt  in  its  recess. 

To  Open  the  Breech. — First  release  the  locking  bolt  from  its  seat 
in  the  block  by  pressing  downward  on  its  handle.  The  crank  is  then 
turned  continuously  towards  the  muzzle,  until  the  tray  comes  to  rest 
against  the  hinge.  As  the  crank  is  turned,  the  teeth  of  the  compound 
gear,  working  in  those  of  the  rotating  rack,  cause  the  block  to  rotate 
to  the  left  until  its  guide  grooves  are  opposite  the  guide  rails  of  the 
tray.  In  this  position  the  lower  shoulder  on  the  lug  strikes  the  lower 
surface  of  the  gear,  preventing  further  rotation  of  the  block.  The 
teeth  of  the  gear  then  engage  in  the  translating  rack,  and  the  block 
is  withdrawn.  At  the  end  of  its  travel  it  strikes  the  inclined  surface 
on  the  rear  toe  of  the  tray  latch,  forcing  it  down  against  the  action  of 
the  latch  spring,  thus  unlatching  the  tray.  The  front  toe  of  the  latch 
then  rises  and  engages  in  its  groove  in  the  block;  the  locking  bolt 
moves  forward  and  enters  its  seat  in  the  latch,  forcing  the  operating 
stud  to  the  front.  The  block  is  prevented  from  moving  to  the  rear 
on  the  tray  by  the  bearing  of  the  guide  rails  against  the  shoulders 
of  the  guide  grooves,  and  from  moving  forward,  by  the  front  toe  of 
the  latch.  The  block  and  tray  swing  with  the  hinge  pin  to  the  right, 
until  the  tray  rests  against  the  hinge.  In  this  position  the  crank 
handle  is  horizontal  and  in  front  of  the  shaft,  the  weight  of  the  frame 
being  sufficient  to  retain  the  block  and  tray  in  place,  without  a  back 
or  securing  latch. 

To  Close  the  Breech. — The  crank  is  turned  to  the  rear,  until  the 
projecting  shoulder  on  the  upper  surface  of  the  rotating  lug  strikes 
the  gear.  As  the  block  is  locked  to  the  tray,  turning  the  crank  to  the 


130  THE  SERVICE  OF  COAST  ARTILLERY 

rear  swings  both  block  and  tray  to  the  left  until  the  tray  strikes  the 
breech  of  the  gun.  The  operating  stud,  projecting  through  the  front 
of  the  latch,  being  pressed  back  by  bearing  against  the  breech,  forces 
the  locking  bolt  into  its  recess  and  releases  the  tray  latch  in  front. 
The  first  small  forward  motion  of  the  block  when  the  tray  strikes  the 
breech  releases  the  rear  toe  of  the  latch,  and  the  latch  spring  forces 
the  hook  over  the  catch,  thus  locking  the  tray  to  the  breech.  The 
block  now  being  free  to  move  forward,  is  forced  home  by  the  translating 
rack  and  gear  and  rotated  to  the  right  by  the  rotating  lug  and  gear, 
until  in  the  firing  position  again,  when  the  projection  on  the  upper  surface 
of  the  lug  strikes  the  gear,  preventing  further  motion. 

To  Assemble  the  Breech  Mechanism. — The  breech  recess,  also  all 
surfaces  of  contact  with  parts  of  the  breech  mechanism,  will  be  care- 
fully cleaned  and  any  traces  of  rust  removed. 

All  parts  of  the  breech  mechanism  will  be  carefully  cleaned  also. 

In  assembling  the  breech  mechanism,  the  worm  shaft  with  its 
ball  bearings  will  be  put  into  place  first.  Insert  one  ball  bearing 
into  seat  at  inner  end  of  worm  recess.  Assemble  other  ball  bearing 
on  worm  shaft  outside  of  worm  and  insert  worm  shaft  with  this  ball 
bearing  into  recess.  Then  put  the  threaded  bronze  bushing  into  place 
and  screAV  entirely  home,  when  its  collar  will  be  in  perfect  contact  with 
the  hinge  plate. 

The  tray  (console)  will  be  assembled  next,  with  its  ball  bearing 
tray  latch,  and  catch  bolt.  The  hinge  pin  will  be  slipped  into  place 
to  support  the  tray  and  allow  it  to  be  swung  into  position  to  receive 
breechblock.  The  obturating  spindle  with  the  gas-check  pad,  split 
rings,  and  disk  will  be  removed  from  the  breechblock  so  that  block 
can  be  suspended  by  a  rope  sling  through  hole  in  breechblock.  This 
rope  sling  to  be  hung  from  a  gin  or  crane  erected  for  the  purpose. 

The  breechblock  will  be  hoisted  until  its  guide  grooves  are  opposite 
the  guide  rails  of  the  tray,  and  will  be  pushed  on  from  the  front  of  tray 
(as  stops  would  prevent  the  opposite),  taking  care  that  the  breech- 
block is  horizontal. 

Note  that  in  the  12-inch  rifle  the  tray  must  be  rotated  till  its  front 
surface  is  parallel  to  the  axis  of  the  gun  when  the  block  is  being  slid 
into  place,  as  otherwise  the  rear  of  block  would  not  clear  the  upper 
hinge  lug  when  the  block  is  well  in  the  recess. 

Disengage  the  rope. 

Swing  tray  with  block  against  end  of  gun,  push  the  block  into 
breech  recess  of  gun,  shoving  it  entirely  home,  but  do  not  rotate  it. 

The  tray  should  now  be  supported  by  blocking  or  otherwise,  so 


OF   THE 

UNIVERSITY 

OF 


ARMAMENT  131 

that  the  hinge  pin  may  be  withdrawn.  After  which  hold  in  position 
the  spiral  gear  with  the  face  having  cylindrical  hub  uppermost,  the  two 
teeth  marked  .4.  and  B  being  inserted  into  spaces  marked  A  and  B  on 
rotating  rack  of  block.  The  vertical  line  engraved  on  the  spiral  gear 
must  now  be  coincident  with  that  on  the  upper  hinge  lug.  Insert 
hinge  pin  with  vertical  line  thereon  coincident  with  above  and  lower 
gently  through  spiral  gear  and  tray  and  lower  hinge  lug,  but  not  below 
the  latter.  Hold  in  this  position  while  bronze  worm  wheel  is  put  into 
place,  as  follows:  The  worm  wheel  has  upper  face  marked  "Top," 
and  the  marked  spaces  on  wheel  must  engage  the  similarly  marked 
teeth  of  the  worm.  The  worm  wheel  should  now  be  rotated  by  the 
worm  (so  that  proper  engagement  of  teeth  is  preserved)  until  the  line 
engraved  upon  the  wheel  coincides  with  the  before-mentioned  vertical 
line  of  hinge  lugs  and  spiral  gear  and  hinge  pin.  Then  hinge  pin  can 
be  lowered  completely  into  place,  and  nut  at  bottom  screwed  on,  and 
the  locking  pin  driven  through  nut  and  hinge  pin. 

The  crank  handle  should  be  placed  upon  the  worm  shaft  in  the 
position  indicated  by  the  engraved  line  and  the  set  screw. 

The  insertion  and  securing  of  the  spindle  will  be  performed  as 
follows:  With  the  breechblock  in  loading  position,  the  spindle,  with 
split  rings,  gas-check  pad,  and  gas-check  disk  upon  it,  will  be  inserted 
into  the  block.  The  large  ball  bearing  will  be  put  in  place  upon  rear 
end  of  spindle  projecting  through  block,  and  spindle  secured  by 
screwing  up  by  hand  the  spindle  nut. 

The  adjustment  of  the  spindle  is  the  same  as  described  for  model 
of  1888  guns. 

To  Remove  and  Dismount  the  Breech  Mechanism. — The  operations 
are  the  reverse  of  those  given  above. 

The  maximum  elevation  of  the  carriage  is  15  degrees,  corresponding 
range,  14,062  yards. 

10-lNCH   BREECH-LOADING   RIFLE,  MODEL  OF  1900 

This  is  the  latest  type  of  10-inch  rifle.  It  is  similar  in  construction 
to  the  model  of  1895,  and  differs  only  in  the  following  points: 

Total  length  420  inches;  weight  34  tons;  length  of  bore  40 
calibers.  The  first  guns  constructed  of  this  model  had  rifling  consisting 
of  60  grooves;  twist,  one  turn  in  50  calibers  to  one  turn  in  25  calibers. 
The  later  guns  of  this  model  have  90  grooves;  twist,  increasing  from 
0  to  1  caliber.  The  powder  chamber  is  made  cylindro-cenical,  instead 
of  cylindrical,  as  in  all  other  types  of  this  caliber. 


132  THE  SERVICE  OF  COAST  ARTILLERY 

Weight  of  propelling  charge,  nitro-cellulose  powder,  205  pounds; 
weight  of  igniter  charge  4  pounds;  weight  of  bursting  charge,  gun 
cotton,  A.P.  shell  22.4  pounds;  A. P.  shot  7.5  pounds. 

Muzzle  velocity  2,250  foot-seconds.  Muzzle  energy  26,169  foot- 
tons. 

Maximum  pressure  38,000  pounds  per  square  inch.  Maximum 
elevation  permitted  by  the  carriage  12  degrees;  corresponding  range 
14,162  yards.  Penetration  in  Krupp  cemented  armor,  at  5,000  yards, 
11.6  inches. 


8-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1888 

This  rifle  is  one  of  the  earliest  models  of  the  built-up  forged  steel 
type,  and  was  for  that  reason  taken  as  an  example  and  described  in 
detail  in  the  chapter  on  Gunnery  and  Ballistics. 

Total  length  278.52  inches;  weight  14.50  tons;  length  of  bore 
32  calibers.  The  bore  has  48  grooves;  twist  of  rifling,  one  turn  in  50 
calibers  to  one  turn  in  25  calibers.  Weight  of  projectile,  capped, 
316  pounds;  weight  of  propelling  charge,  nitro-cellulose  powder,  80 
pounds;  weight  of  igniter  charge  1.5  pounds;  weight  of  bursting 
charge,  gun  cotton,  A.P.  shell  11.5  pounds;  A.P.  shot  4  pounds. 

Muzzle  velocity  2,200  foot-seconds;  Muzzle  energy  10,683  foot- 
tons.  Maximum  pressure  38,000  pounds  per  square  inch.  Maximum 
elevation  permitted  by  the  carnage  12  degrees;  corresponding  range 
11,019  yards.  Penetration  in  Krupp  cemented  armor,  at  5,000 
yards,  6.8  inches. 


8-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1888  Mi 


This  rifle  is  similar  in  construction  and  power  to  the  Model  of  1888, 
.and  differs  only  in  the  following  points: 

5  C  hoops.     The  size  of  the  D  hoops  altered  slightly. 

8-lNCH  BREECH-LOADING  RIFLE,  MODEL  OF  1888  Mil 

This  rifle  is  similar  in  construction  and  power  to  the  model  of  1888 
Mi,  and  differs  only  in  the  following  points: 

2  C  hoops;  1  D  hoop;  4  A  hoops.  Jacket  increased  slightly  in 
length.  Bronze  breech  plate. 


OF   THE 

UNIVERSITY 

OF 


ARMAMENT  133 


INTERMEDIATE  ARMAMENT 

6-lNCH    QUICK-FIRING    ARMSTRONGS  GUN 

(See  Plates  XI  and  XII) 

This  rifle  is  manufactured  by  the  W.  G.  Armstrong  Company, 
England.  It  consists  of  a  tube,  jacket,  2  C  hoops,  1  A  hoop,  1  D  hoop, 
and  a  breech  ring. 

It  is  constructed  entirely  of  steel,  and  is  designed  for  obtaining 
great  rapidity  of  fire.  For  this  purpose  it  is  mounted  on  a  special 
mounting,  and  is  not  provided  with  trunnions,  but  is  carried  by  a 
cradle  which  encircles  the  gun,  and  in  which  it  slides  when  recoiling. 
This  cradle  is  provided  with  trunnions  on  which  the  gun  and  cradle 
are  balanced.  The  breech  of  the  gun  is  surrounded  by  a  breech  ring 
which  has  a  projecting  arm  on  it  for  connecting  the  gun  with  the  recoil 
cylinder,  which  forms  part  of  the  cradle.  The  mechanism  for  closing 
the  breech  is  of  the  interrupted-screw  system,  so  arranged  that  it 
can  be  quickly  opened  or  closed  by  a  single  movement.  The  gun  is 
provided  with  electrical  firing  gear,  connected  with  an  electrical  pistol, 
fixed  to  the  mounting  in  a  convenient  place,  so  that  the  man  laying 
the  gun  can  fire  while  looking  over  the  sights.  It  is  also  provided  with 
a  percussion  arrangement  for  mechanical  firing  in  case  of  failure  of  the 
electrical  gear.  The  gun  sights  are  fixed  to  the  gun  cradle,  and  do 
not  therefore  recoil  with  the  gun.  The  powder  is  contained  in  a  metallic 
cartridge  case,  the  base  of  the  projectile  resting  against  the  front  end 
of  this  case. 

Breech  Mechanism  (Plate  XII) . — The  breech  of  the  gun  is  closed  by 
a  screw  formed  in  two  steps,  the  front  step  being  tapered  and  of  less 
diameter  than  the  rear;  both  steps  have  three  portions  of  their  threads 
removed,  each  one-sixth  of  a  turn,  the  threads  on  one  step  standing 
opposite  to  the  blank  spaces  on  the  other;  this  arrangement  distributes 
the  strain  all  round  the  circumference  of  the  breech  screw.  The 
interior  of  the  gun  at  the  breech  is  prepared  in  a  similar  manner,  and 
admits  of  the  breech  screw  being  swung  into  place  and  locked  by  a 
simple  mechanism  to  be  described. 

The  breech  screw  is  supported  by  a  carrier,  on  which  it  is  free  to 
revolve  through  an  angle  of  60  degrees;  the  carrier  is  hinged  to  the 
right  side  of  the  breech  ring,  so  that  the  screw  can  swing  clear  of  the 
breech  opening  for  loading.  The  screw  is  secured  on  the  carrier  by 
means  of  the  stop  bolt.  The  breechblock  is  unscrewed  and  with- 


134  THE  SERVICE  OF  COAST  ARTILLERY 

drawn  from  the  gun  by  a  single  horizontal  movement  of  the  hand- 
locking  lever,  which  is  pivoted  on  the  right  side. 

A  projecting  pin  is  screwed  into  the  rear  face  of  the  breech  screw, 
and  enters  a  traversing  bush  in  the  sliding  block.  This  block  slides 
in  a  seat  in  the  carrier,  and  is  connected  to  the  hand-locking  lever 
by  the  link.  When  the  breech  is  open  the  screw  is  prevented  from 
turning  on  the  carrier  by  a  spring  catch  on  the  carrier,  which  engages 
a  notch  in  the  screw  as  it  is  withdrawn  from  the  gun;  when  closing 
the  breech  the  catch  comes  in  contact  with  the  face  of  the  gun,  thus 
releasing  the  screw  and  leaving  it  free  to  be  screwed  home. 

It  is  impossible  to  fire  the  gun  until  the  breech  is  completely  locked. 
This  is  insured  by  means  of  a  safety  gear  consisting  of  a  pawl  fitted 
to  a  spindle.  The  pawl  engages  a  lip  on  the  striker,  and  prevents  the 
latter  from  touching  the  primer  while  the  hand  lever  is  in  the  unlocked 
position.  On  the  lower  end  of  the  spindle  is  formed  a  lever  with  a 
projection  which  engages  in  a  recess  on  the  hand  lever.  Another  pro- 
jection is  formed  on  the  lever,  which  is  acted  upon  by  the  sliding  block 
so  that  the  pawl  is  retained  in  position  by  a  key  on  the  spindle  falling 
into  a  notch  in  the  carrier,  while  the  hand  lever  is  drawn  clear  in 
unscrewing  the  breechblock. 

When  the  hand  lever  is  in  the  locked  position,  it  is  held  there  by 
the  torsion  of  the  spiral  spring  when  the  gun  is  elevated. 

The  striker  is  secured  in  the  carrier  by  a  retaining  nut,  and  can  be 
readily  removed  by  slightly  withdrawing  it  and  turning  the  nut  a  quarter 
of  a  turn. 

To  fix  the  striker  it  is  pushed  into  the  gun,  and  the  retaining  nut 
turned  to  the  right  or  left. 

Electrical  Firing  Gear. — This  gear  consists  of  an  insulated  firing 
needle  fitted  in  the  axis  of  the  breech  screw.  The  needle  is  surrounded 
by  a  spiral  spring,  which  holds  it  against  the  electrical  primer  in  the 
base  of  the  cartridge  case.  The  needle  is  provided  with  a  projection 
at  the  rear  end  by  which  it  is  drawn  back,  the  projection  being  acted 
upon  by  a  lever  on  the  spindle.  On  the  lower  end  of  the  spindle  is 
fitted  a  pawl,  having  a  projecting  piece  on  the  under  side,  which  is 
held  in  a  cam  groove  cut  in  the  hand  lever.  When  the  hand  lever 
is  moved  away  from  the  locked  position,  the  spindle  is  revolved  b}^  its 
projecting  piece  working  in  the  cam  groove,  thus  causing  the  pawl 
to  engage  the  projection,  and  draw  the  needle  back  a  sufficient  distance 
to  effectually  prevent  it  from  making  a  contact  with  an  electric  primer. 

Two  brackets  are  provided,  one  fitted  to  the  gun,  while  the  other 
is  fitted  to  the  gun  cradle.  These  brackets  carry  the  insulated  electric 


1 


ARMAMENT  135 

cable  and  the  contact  pieces  on  the  ends  of  these  cables,  the  contact 
pieces  being  forced  out  by  springs  so  that  their  contact  is  always 
insured.  The  cable  from  the  needle  passes  to  the  bracket  on  the  gun, 
and  there  contact  is  made  through  the  contact  pieces  to  the  cable 
attached  to  the  bracket  on  the  gun  cradle,  which  is  connected  to  the 
electric  firing  pistol.  This  pistol  is  fitted  to  the  mounting  in  a  con- 
venient position  for  the  man  who  lays  and  fires  the  gun.  A  three-cell 
electric  battery  is  placed  on  the  mounting;  one  of  the  terminals 
of  this  battery  is  connected  to  the  pistol  and  the  other  to  the  mounting 
as  an  earth  connection.  The  brackets  are  detachable  and  can  be 
easily  removed,  which  allows  a  spare  cable  to  be  readily  applied  if 
required. 

An  alternative  electrical  firing  gear  is  also  provided,  which  can  be 
immediately  put  into  action  if  the  other  one  becomes  short  circuited 
or  the  insulation  fails.  It  consists  of  a  long  cable,  having  a  split  pin 
at  one  end,  which  is  pushed  into  a  hole  in  the  head  of  the  needle.  The 
other  end  is  connected  to  the  terminal  of  the  battery.  About  the 
middle  of  the  cable  is  a  firing  key,  which  is  held  in  the  hand  of  the 
man  who  lays  the  gun.  On  pushing  down  the  end  of  this  firing  key 
the  circuit  is  completed  and  the  current  passes  direct  from  the  battery 
to  the  needle,  and  thus  fires  the  gun. 

Before  connecting  this  alternate  cable  to  the  battery  and  the 
needle,  the  parts  of  the  other  cables,  which  are  connected  to  the  battery 
and  the  needle,  should  be  removed. 

Percussion  Firing  Gear. — This  gear  is  fitted  to  the  retaining  nut,  and 
consists  of  a  spring  trigger  with  loop  to  receive  the  lanyard. 

To  fire  by  percussion  the  firing  pin  or  needle  is  pulled  to  the  rear 
until  it  is  caught  by  the  trigger,  which  retains  it  until  the  latter  is 
displaced  by  the  -lanyard  attached  to  the  trigger  loop.  This  leaves 
the  firing  needle  free  to  travel  forward  and  strike  the  primer. 

When  firing  with  this  gear  the  adapter  is  screwed  into  the  base  of 
the  cartridge  case  and  the  percussion  primer  placed  into  its  chamber 
in  the  adapter. 

When  the  trigger  is  displaced  the  projection  on  the  head  of  the 
trigger  is  moved  into  a  slot  provided  in  the  carrier,  which  prevents 
the  retaining  nut  from  being  turned  if  the  lanyard  is  pulled  in  an 
upward  direction. 

Cartridge  Extractor. — The  cartridge  is  started  by  the  extractor, 
which  only  has  sufficient  motion  to  insure  its  being  free  for  the  remainder 
of  the  extraction,  the  conical  shape  of  the  cartridge  case  and  chamber 
rendering  a  small  motion  sufficient  for  this  purpose.  The  cartridge 


136  THE  SERVICE  OF  COAST  ARTILLERY 

is  then  completely  withdrawn  and  laid  in  the  recess  by  means  of  a  hand 
extractor,  which  readily  fits  over  and  firmly  holds  the  primer. 

The  mechanical  extractor  is  worked  by  the  carrier  in  opening 
the  breech  screw.  It  consists  of  a  lever  passing  through  one  side  of 
the  gun  and  fitting  into  the  groove  for  the  rim  of  the  cartridge  case 
in  such  a  manner  that  when  it  is  turned  about  its  own  axis  the  fitted 
part  acts  as  a  lever  and  presses  the  cartridge  to  the  rear. 

The  extractor  is  brought  back  into  its  place  as  the  breech  is  closed 
by  means  of  a  strong  helical  spring  outside  the  gun.  This  spring  also 
serves  as  a  buffer  to  prevent  the  breech  screw  and  carrier  being  swung 
too  violently  around.  The  extractor  is  fitted  on  the  right-hand  side, 
so  that  it  is  out  of  the  way  of  loading  or  damage  from  a  projectile 
when  the  latter  is  being  entered  into  the  gun. 

The  bore  has  24  grooves;  twist,  from  0  to  1  in  30  calibers.  The 
powder  chamber  is  conical. 

Total  length  249.1  inches;  weight  6.6  tons;  length  of  bore  40 
calibers;  weight  of  projectile  106  pounds;  weight  of  propelling  charge, 
nitro-cellulose  powder  19  pounds;  Cordite  13.3  pounds;  weight  of 
bursting  charge,  Maximite  or  Explosive  D,  4.3  pounds. 

Muzzle  velocity  2,150  foot-seconds.  Muzzle  energy  3,400  foot- 
tons.  Maximum  pressure  34,000  pounds  per  square  inch.  Maximum 
elevation  permitted  by  the  carriage  16  degrees;  corresponding  range 
10,185  yards.  Penetration  in  Krupp  cemented  armor,  at  5,000  yards, 
2.9  inches. 


6-lNCH  RAPID-FIRE  GUN,  MODEL  OF  1897 
(See  Modification  I) 

6-lNCH  RAPID-FIRE  GUN,  MODEL  OF  1897,  Mi 
(Ordnance  Department  Model) 

This  rifle  follows  the  general  method  of  built-up  forged-steel  con- 
struction. It  is  of  American  manufacture.  It  consists  of  a  tube, 
jacket,  4  A  hoops  (one  of  which  is  the  trunnion  hoop),  2  C  hoops,  1  D 
hoop.  The  powder  chamber  is  cylindrical. 

The  breech  mechanism  consists  of  the  breechblock,  gear  segment, 
block  carrier,  lever,  pinion,  latch,  obturator,  and  associate  parts. 

The  breechblock  is  cylindrical,  with  an  axial  hole  for  the  reception 
of  the  spindle  and  washer.  The  front  part  of  the  block  for  a  short 
distance  back  is  reduced  in  diameter.  This  reduced  part  or  nose  of 


ARMAMENT  137 

the  block  leaves  a  space  in  the  breech  recess  of  the  gun,  in  which  fouling 
may  collect  without  interrupting  the  working  of  the  block. 

On  the  outer  surface  of  the  block  is  cut  a  V-shaped  screw  thread 
with  rounded  top  and  bottom.  This  screw  thread  is  divided  circum- 
ferentially  into  eight  equal  parts,  and  the  threads  cut  from  the  alternate 
sectors.  The  sectors  from  which  the  threads  are  cut  are  called  the 
slotted  sectors,  and  permit  the  entry  of  the  block  past  the  correspond- 
ing threaded  sectors  in  the  breech  recess.  The  threaded  sectors  of  the 
block  are  then  engaged  with  the  threaded  sectors  of  the  recess  by 
revolving  the  block  through  an  angle  of  45  degrees  about  its  longi- 
tudinal axis.  Portions  of  the  threaded  sectors  on  the  block  are  cut 
away  and  parts  of  the  slotted  sectors  deepened  to  provide  clearance 
between  the  block  and  breech  recess  when  the  former  is  swung  to  or 
from  the  piece. 

The  rear  end  of  the  block  is  turned  down  to  a  smaller  diameter, 
and  the  cylindrical  surface  thus  formed  is  prolonged  into  the  block 
and  increased  in  length  by  means  of  an  annular  groove  cut  in  the 
rear  face  of  the  block.  This  cylindrical  surface  is  called  the  guide 
cylinder,  and  the  annular  groove,  the  guide  groove  of  the  block.  That 
portion  of  the  rear  face  of  the  block  which  lies  outside  of  the  guide 
groove  is  called  the  stop  flange.  When  the  block  is  withdrawn  the 
stop  flange  strikes  the  bottom  of  the  stop  groove  in  the  block  carrier 
and  limits  the  rearward  motion  of  the  block.  The  guide  cylinder 
supports  the  breechblock  in  the  carrier  and  guides  it  in  its  motions  of 
rotation  and  translation.  The  guide  flange  of  the  block  carrier  fits 
into  the  guide  groove  of  the  block  and  assists  in  supporting  and  guiding 
the  latter.  Four  oil  holes  are  drilled  radially  from  the  exterior  of 
the  block  to  the  bottom  of  the  guide  groove  to  facilitate  oiling  the  bear- 
ing surfaces.  These  holes  also  act  as  air  vents.  An  oil  hole  cut  radially 
in  the  nose  of  the  block  and  closed  by  a  screw  is  provided  for  oiling 
the  front  face  of  the  block. 

The  locking  recess  is  cut  in  the  surface  of  the  guide  cylinder.  The 
depth  of  this  locking  recess  gradually  increases  from  rear  to  front, 
beginning  at  zero  at  the  rear  and  terminating  at  the  front  end  in  a 
well,  called  the  locking  recess.  When  the  block  is  withdrawn  the  inner 
end  of  the  latch  bolt  drops  into  the  locking  recess  and  locks  the  block 
positively  to  the  block  carrier. 

The  gear  segment  is  attached  to  the  rear  end  of  the  breechblock 
by  a  spline  and  two  screws.  It  consists  essentially  of  a  segment  of 
a  bevel  gear  and  a  short  rack,  which  mesh  with  a  pinion  pivoted  on 
the  block  carrier  and  actuated  by  the  lever.  Part  of  the  periphery 


138  THE  SERVICE  OF  COAST  ARTILLERY 

of  the  pinion  is  cut  into  a  bevel  gear  and  another  part  into  a  pinion, 
meshing  with  the  corresponding  parts  of  the  gear  segment.  The 
bevel-gear  parts  rotate  the  block  and  the  rack-and-pinion  parts  trans- 
late it.  These  motions  are  successive;  the  termination  of  the  motion 
of  rotation  in  opening  the  breech  brings  the  rack  and  pinion  into  the 
proper  position  to  withdraw  the  block,  and  the  termination  of  the 
motion  of  translation  in  closing  the  breech  brings  the  bevel-gear  seg- 
ments into  mesh  to  rotate  it. 

The  block  carrier  is  a  steel  casting  pivoted  by  means  of  a  hinge  pin 
to  a  hinge  plate  attached  to  the  jacket  on  the  right  side  of  the  breech. 
As  its  name  indicates,  its  principal  office  is  to  support  the  block  in  its 
various  movements.  It  is  bored  to  take  the  breechblock  guide  cylinder. 
On  the  front  face  of  the  carrier  surrounding  this  bore  is  a  projecting 
ring  called  the  guide  flange  which  enters  the  guide  groove  of  the  block 
and  assists  in  supporting  and  guiding  it.  An  annular  groove,  called 
the  stop  groove,  cut  in  the  front  face  of  the  carrier  at  the  base  of  the 
guide  flange,  increases  the  length  of  the  latter,  and  forms  a  stop  against 
which  the  stop  flange  of  the  breechblock  strikes,  limiting  the  motion 
of  the  block  to  the  rear. 

A  lug  projects  to  the  rear  from  the  lower  part  of  the  block  carrier 
and  forms  a  seat  for  the  pinion.  The  latter  is  mounted  on  this  seat 
upon  a  pivot  in  the  form  of  a  screw  bolt  which  passes  through  the 
pinion  and  screws  into  the  lug.  This  screw-bolt  pivot  is  prevented 
from  unscrewing  by  the  pivot  nut  which  is  screwed  on  it  under  the 
lug.  The  lever  for  actuating  the  pinion  is  fitted  upon  a  square 
extension  upon  the  latter.  The  free  end  of  the  lever  terminates  in  a 
vertical  handle. 

The  latch  is  a  locking  device  for  the  block  carrier.  It  consists 
of  the  lock  bolt,  latch  spring,  latch  lever,  and  latch-lever  pivot,  mounted 
in  the  block  carrier,  and  the  latch-bolt  seat  and  tripping  stud  secured 
to  the  breech  face  of  the  piece  by  screws.  The  latch  bolt  lies  in  a 
radial  hole  drilled  through  the  block  carrier.  The  end  of  the  bolt 
nearer  the  axis  of  the  block  is  tapered  to  facilitate  its  entering  the 
locking  recess  in  the  breechblock  guide  cylinder.  It  is  also  slightly 
beveled  on  the  end  so  that  it  will  the  more  easily  ride  out  of  the  locking- 
recess  and  up  the  inclined  bottom  of  the  groove.  The  outer  end  of 
the  bolt  has  a  mortise  cut  through  it  in  which  one  end  of  the  latch 
lever  works.  This  end  of  the  latch  bolt  is  also  slightly  beveled  to  make 
it  ride  out  of  the  latch-bolt  seat.  The  latch-bolt  seat  is  a  lug  secured 
to  the  breech  face  by  two  screws.  (There  are  a  few  guns  in  service 
having  the  latch-bolt  seat  and  tripping  stud  in  the  form  of  screw 


ARMAMENT  139 

bolts  screwed  directly  into  the  breech  face  of  the  piece.)  Through  it 
is  drilled  a  radial  hole  into  which  the  latch  bolt  enters  when  the  carrier 
is  against  the  breech  of  the  piece. 

The  latch  lever  is  pivoted  in  a  circumferential  slot  cut  in  the  exterior 
surface  of  the  carrier.  The  latch-lever  pivot  is  a  small  screw  bolt 
inserted  from  the  outer  base  of  the  carrier.  One  end  of  the  lever 
works  in  the  mortise  in  the  latch  bolt;  the  other  end  is  broadened, 
forming  a  shoulder  against  which  a  spiral  spring,  called  the  latch-lever 
spring,  bears.  This  spring  is  compressed  between  the  block  carrier 
and  the  latch-lever  shoulder,  by  means  of  the  tripping  stud.  This 
operation  withdraws  the  latch  bolt  from  the  breechblock.  When  the 
block  is  swung  away  from  the  breech,  the  inner  end  of  the  latch  bolt 
rests  in  the  locking  recess  and  locks  the  block  to  the  carrier.  In  this 
position  the  upper  end  of  the  latch  lever,  against  which  the  spring 
bears,  projects  slightly  beyond  the  exterior  surface  of  the  carrier. 
In  closing  the  breech,  just  before  the  carrier  comes  in  contact  with 
the  breech  face  of  the  piece,  this  projecting  part  of  the  lever  strikes 
the  beveled  surface  of  the  tripping  stud  and  is  forced  toward  the  axis 
of  the  block.  This  motion  of  the  lever  lifts  the  latch  lock  from  the 
locking  recess  and  leaves  the  block  free  to  be  translated  through  the 
block  carrier. 

The  tripping  stud  is  a  lug  secured  to  the  breech  face  by  two  screws. 
Its  inner  face  is  beveled  so  as  to  trip  the  latch  as  just  explained.  The 
complete  action  of  the  latch  is  as  follows:  With  the  breech  closed,  the 
outer  end  of  the  latch  bolt  rests  in  the  latch-bolt  seat,  locking  the 
block  carrier  to  the  breech  face;  the  inner  end  of  the  latch  bolt  bears 
against  the  guide  cylinder  of  the  block  and,  at  the  end  of  the  motion 
of  rotation  of  the  block  in  opening  the  breech,  rests  in  line  with  the 
end  of  the  latch  groove.  When  the  block  is  withdrawn  the  bolt  rides 
down  the  inclined  bottom  of  the  latch  groove  and  its  outer  end  is 
withdrawn  from  the  latch-bolt  seat,  freeing  the  block  carrier  from 
the  breech.  At  the  end  of  the  motion  of  withdrawal  the  inner  end  of 
the  latch  bolt  enters  the  locking  recess  in  the  breechblock.  As  the  bolt 
carrier  is  swung  away  from  the  piece  the  end  of  the  latch  lever  clears 
the  tripping  stud  so  that  the  full  force  of  the  latch  spring  comes  into 
play  and  the  latch  bolt  is  forced  to  the  bottom  of  the  locking  recess, 
securely  locking  the  block  to  the  carrier.  In  closing  the  breech  the 
action  of  the  latch  is  the  reverse  of  that  just  given. 

With  breech  open  the  block  is  locked  to  the  carrier.  As  the  latter 
is  swung  against  the  breech  face,  the  tripping  stud,  by  means  of  the 
lever,  raises  the  latch  bolt  far  enough  from  the  bottom  of  the  latch- 


140  THE  SERVICE  OF  COAST  ARTILLERY 

groove  locking  recess  for  the  end  of  the  bolt  to  ride  on  the  inclined 
bottom  of  the  groove  as  the  block  is  moved  forward  through  the  block 
carrier.  As  the  bolt  rides  up  the  inclined  bottom  of  the  latch  groove 
its  outer  end  enters  the  latch-bolt  seat  and  locks  the  block  carrier  to 
the  breech  face. 

The  obturator  is  composed  of  the  following  parts:  The  spindle, 
front  and  rear  exterior  split  rings,  interior  split  ring,  pad,  filling-in 
disk,  spindle  nut,  and  spindle-ball  washer. 

The  object  of  the  obturator  is  to  prevent  the  escape  of  gas  from 
the  powder  chamber  to  the  rear  during  firing,  and  to  transmit  to  the 
breechblock  the  stress  of  firing  resulting  from  pressure  of  gases  upon 
the  bottom  of  the  bore. 

The  spindle  is  mounted  in  the  block  in  the  spindle  recess,  the  rear 
end  of  the  stem  is  threaded  for  the  spindle  nut,  while  the  front  end  is 
enlarged  into  a  mushroom-shaped  head  which  forms  the  bottom  of  the 
bore  of  the  gun. 

The  vent  is  axial  and  is  drilled  through  the  spindle.  A  copper 
bushing,  forced  into  an  undercut  in  the  face  of  the  mushroom  head, 
protects  the  vent  from  erosion  and  enables  repairs  to  be  easily  made. 
In  passing  through  this  copper  plug  the  vent  is  reduced  in  diameter, 
and  the  rear  end  of  the  vent  is  formed  into  a  primer  seat  to  take  the 
primer  used  to  ignite  the  charge. 

The  split  rings  are  of  steel  accurately  finished,  and  split  diagonally 
through  one  side.  The  exterior  ones  are  made  of  slightly  greater 
diameter  than  the  gas-check  seat  in  the  gun  and  are  sprung  into  place. 
The  interior  one  is  slightly  smaller  than  its  seat  on  the  spindle.  The 
filling-in  disk  is  a  steel  washer  interposed  between  the  gas-checking 
device  and  the  front  face  of  the  breechblock.  A  slight  shoulder  on 
the  rear  face  of  the  mushroom  head  supports  and  centers  the  front 
split  ring.  The  rear  split  ring  is  similarly  held  by  an  offset  on  the  front 
face  of  the  filling-in  disk. 

The  gas-check  pad  is  a  disk  of  asbestos  and  tallow,  compressed 
under  heavy  pressure  and  covered  with  canvas.  It  forms  a  yielding 
medium  for  the  transmission  of  pressure  to  the  block.  Under  the 
pressure  of  firing  the  plastic  nature  of  the  pad  causes  it  to  press  outward 
toward  the  gas-check  seat  and  inward  against  the  spindle,  forcing  the 
split  rings  firmly  against  their  seats  and  completely  stopping  the  passage 
of  gas. 

The  spindle-ball  washer  consists  of  two  steel  rings  with  a  groove 
cut  in  one  face  of  each  ring  to  form  a  pocket  for  twenty  f-inch  hardened- 
steel  balls.  The  rings  with  the  balls  between  them  are  held  together 


ARMAMENT  141 

by  a  cylinder  of  ^-inch  copper,  which  lines  the  bore  of  the  rings  and 
has  its  ends  flanged  outward  over  their  end  faces.  The  washer  is 
interposed  between  the  spindle  nut  and  the  breechblock  and  reduces 
the  friction  between  them  when  the  block  is  rotated. 

The  spindle  nut  is  screwed  on  the  rear  end  of  the  stem  of  the 
spindle,  and  holds  the  spindle  in  its  position  in  the  block.  It  is  turned 
on  the  exterior,  provided  with  a  screw-driver  slot,  and  plainly  stamped 
to  indicate  direction  of  unscrewing. 

The  spindle  key  extends  radially  downward  through  the  carrier 
and  block,  and  its  inner  end  enters  a  longitudinal  slot  cut  in  the  stem 
of  the  spindle.  It  acts  as  a  stop  for  limiting  the  rotation  of  the  block, 
and  also  prevents  the  spindle  from  turning. 

A  slot  is  cut  in  the  guide  cylinder  in  which  the  key  moves  during 
the  rotation  of  the  block,  and  thus  the  firing  mechanism  is  always 
held  in  an  upright  position. 

To  Open  the  Breech. — With  the  block  closed  the  lever  lies  parallel 
to  the  face  of  the  breech,  with  handle  to  the  left.  Moving  the  handle 
to  the  rear  and  right,  describing  an  arc  about  the  pinion  pivot  as  a 
center,  rotates  the  block  through  an  angle  of  45  degrees  and  disengages 
the  threaded  sectors  on  the  block  from  those  in  the  breech  recess.  A 
further  movement  of  the  handle  about  the  same  center  draws  the  block 
to  the  rear  until  the  stop  flange  strikes  the  bottom  of  the  stop  groove 
and  the  head  of  the  latch  bolt  comes  opposite  the  locking  recess.  This 
movement  of  the  block  to  the  rear  frees  the  gas  check  from  its  seat 
in  the  gun  sufficiently  to  enable  the  block,  supported  by  the  carrier, 
to  be  swung  out  of  the  recess  and  to  one  side  of  the  piece  about  the 
block-carrier  hinge  pin  as  a  center.  At  the  end  of  the  motion  of 
withdrawal  the  outer  end  of  the  latch  bolt  is  withdrawn  from  its  seat, 
freeing  the  block  carrier  from  the  breech  face  of  the  gun  so  that  a 
further  motion  of  the  lever  handle  to  the  right  swings  the  block  carrier 
and  block  away  from  the  piece.  During  this  movement  the  inner 
end  of  the  latch  bolt  enters  the  locking  recess  in  the  block  and  locks 
the  block  in  position  in  the  block  carrier. 

To  Close  the  Breech. — Move  the  lever  handle  to  the  left  as  far  as 
it  will  go.  The  action  of  the  various  parts  of  the  mechanism  is  the 
reverse  of  that  given  above.  When  the  breech  is  open  it  will  be  noted 
that  the  block  is  locked  to  the  block  carrier  and  that,  until  it  is  unlocked, 
relative  motion  of  the  lever  handle  with  reference  to  the  block  and  carrier 
can  not  occur,  so  that  the  first  movement  of  the  lever  handle  to  the 
left  swings  the  block  into  its  recess  and  the  carrier  against  the  face 
of  the  piece.  The  action  of  the  latch  now  frees  the  block  from  the 


142  THE  SERVICE  OF  COAST  ARTILLERY 

carrier  and  locks  the  latter  to  the  piece.  Further  motion  of  the  lever 
handle  first  forces  the  block  forward  in  the  breech  recess  and  then 
rotates  it  to  its  seat. 

The  movement  of  the  lever  handle  to  open  or  close  the  breech 
above  described  is  one  continuous  motion. 

To  Remove  and  Dismount  Breech  Mechanism. — Detach  firing  cable 
from  contact  piece.  Pull  outward  on  slide  stop  and  lift  slide  from 
housing.  Rotate  operating  lever  until  it  stands  perpendicular  to  the 
face  of  the  breech.  Remove  the  yoke.  The  housing  may  then  be 
withdrawn  to  the  rear,  bringing  with  it  the  safety  lever.  Open  the 
breech.  Remove  the  gear  segment.  Remove  the  breechblock  stop. 
Take  out  the  latch-lever  pivot. and  remove  the  latch-lever  spring  and 
bolt.  The  block  is  then  free  to  be  removed  from  the  carrier.  Drive 
out  the  pivot  pin  and  remove  the  pivot  nut,  unscrew  the  pivot  and  the 
pinion  and  lever  are  then  free  to  be  removed  from  the  carrier.  Drive 
out  the  hinge  pin,  being  careful  to  support  the  carrier  while  doing 
so,  and  the  carrier  is  then  freed  from  the  piece. 

To  Assemble  the  Breech  Mechanism. — The  operations  are  the  reverse 
of  those  given  above. 

Total  length  277.85  inches;  weight  7.25  tons;  length  of  bore 
44.6  calibers.  The  bore  has  36  grooves;  twist,  one  turn  in  50  calibers 
to  one  turn  in  25  calibers. 

The  weight  of  the  projectile  is  106  pounds;  weight  of  propelling 
charge,  nitro-cellulose  powder,  29.75  pounds;  weight  of  bursting 
charge,  Maximite  or  Explosive  D,  4.3  pounds.  Maximum  pressure 
38,000  pounds  per  square  inch.  Muzzle  velocity  2,600  foot-seconds. 
Muzzle  energy  4,973  foot-tons.  Maximum  elevation  permitted  by 
carriage  15  degrees;  corresponding  range  11,799  yards.  Penetration 
in  Krupp  cemented  armor,  at  5,000  yards,  3.78  inches. 

6-lNCH  RAPID-FIRE  GUN,  MODEL  OF  1900 
(See  Plates  XIII  and  XIV) 

This  rifle  is  of  Ordnance  Department  manufacture.  It  is  similar 
in  construction  to  the  model  of  1897,  and  differs  only  in  the  following 
points:  2  A  hoops.  Powder  chamber  considerably  larger  in  diameter 
and  shorter  in  length.  Thread  of  the  breechblock  cut  in  a  breech 
bushing,  instead  of  into  the  jacket. 

This  model  of  gun  is  made  in  two  types,  one  for  use  on  disappearing 
carriage  and  the  other  for  rapid-fire  carriage,  the  gun  used  on  the 
former  being  slightly  heavier  than  that  used  on  the  latter. 


OF  THE 

UNIVERSITY 

OF 

=£4  LI  FOR] 


ARMAMENT  143 

Total  length  310.4  inches;  weight  8.5  tons;  length  of  bore  50  calibers. 

The  powder  chamber  is  cylindro-conical.  The  breech  mechanism 
is  the  same  as  that  of  the  model  1897  Mi  excepting  that  the  loading 
tray  pivot  has  a  solid  head  and  is  screwed  into  the  breech  face  of  the 
rifle. 

Weight  of  propelling  charge,  nitro-cellulose  powder,  including 
igniter,  42  pounds ;  weight  of  bursting  charge,  Maximite  or  Explosive 
D,  4.3  pounds.  Muzzle  velocity,  2,600  foot-seconds.  Muzzle  energy 
6,180  foot-tons.  Maximum  pressure  36,000  pounds  per  square  inch. 
Maximum  elevation  permitted  by  carriage,  15  degrees;  corresponding 
range,  13,077  yards.  Penetration  in  Krupp  cemented  armor  at  5,000 
yards,  3.94  inches. 

6-lNCH  RAPID-FIRE  GUN,  MODEL  OF  1903 

This  rifle  is  practically  identical  in  construction  to  the  model 
of  1900,  except  in  breech  mechanism.  It  is  slightly  heavier  for  use 
on  disappearing  carriage. 

The  first  guns  of  this  model  to  be  manufactured  had  the  same  number 
of  grooves  in  the  bore  and  the  same  twist  of  rifling  as  the  model  of  1897 
Mi.  The  later  guns  have  54  grooves,  with  a  twist  of  rifling  0  to  1 
in  25  calibers. 

The  breech  mechanism  consists  of  the  breechblock,  block  carrier, 
operating  spool,  operating  lever,  rack,  latch,  obturator,  loading  tray 
and  associate  parts. 

The  breechblock  is  in  the  form  of  a  truncated  ogive  with  the  interior 
hollowed  out,  forming  a  central  cylindrical  stem,  which  is  prolonged 
beyond  the  rear  face  of  the  block.  Through  the  center  of  the  stem  is 
an  axial  hole  for  the  reception  of  the  obturator  spindle  and  obturator 
spring.  The  front  part  of  the  block  for  a  short  distance  back  is  reduced 
in  diameter,  leaving  a  space  in  the  breech  recess  of  the  gun  in  which 
fouling  may  collect  without  interrupting  the  working  of  the  block. 
On  the  outer  surface  of  the  block  is  cut  a  screw  thread  with  rounded 
top  and  bottom.  The  rear  face  of  the  thread  is  more  inclined  to  the 
surface  than  the  front  thread.  This  screw  thread  is  divided  circum- 
ferentially  into  12  equal  parts,  and  the  thread  cut  from  alternate 
sectors.  A  stop  groove  is  cut  through  the  stem  of  the  block  to  allow 
the  spindle  key  to  pass  into  the  spindle  groove.  The  spindle  key 
thus  serves  the  purpose  of  a  breech  block  stop. 

A  roller  is  attached  to  the  block  by  an  axle  screwed  into  the  block. 
This  roller  works  in  the  roller  groove  of  the  operating  spool  entering 


144  THE  SERVICE  OF  COAST  ARTILLERY 

the  groove  at  the  beginning  of  rotation  in  closing  the  breech,  and 
remaining  in  the  groove  until  the  end  of  the  rotation  in  opening  the 
breech.  The  functions  of  the  roller  are  to  act  as  a  lock  to  prevent  the 
rotation  of  the  block  under  firing  pressure,  to  give  the  slow  arid  powerful 
thrust  to  the  block  at  the  beginning  of  rotation  in  opening  the  breech, 
and  a  complete  rotation  of  the  block  in  closing  the  breech  after  the 
rack  tooth  disengages. 

A  translating  groove  is  cut  in  the  surface  of  the  block.  The  trans- 
lating stud  on  the  opposite  spool  works  in  this  groove,  to  cause  a  trans- 
lation of  the  block.  On  the  rear  end  of  the  breechblock  stem  are  two 
teeth  which  engage  the  teeth  of  the  rack  to  cause  rotation  of  the 
breechblock. 

The  block  carrier  is  pivoted  by  means  of  the  hinge  pin,  to  the  hinge 
lugs  of  the  hinge  plate.  It  is  provided  with  a  central  hub  bored  to 
take  the  stem  of  the  breechblock. 

A  groove  is  cut  in  the  inside  of  the  hub  to  allow  the  teeth  on  the  block 
stem  to  pass  in  assembling.  A  slot  is  cut  through  the  hub  to  permit 
the  spindle  key  to  pass  into  the  stop  groove.  The  upper  end  of  the 
spindle  key  is  held  in  a  slot  cut  in  the  upper  part  of  the  block  carrier. 

The  firing  lever  passes  through,  and  is  pivoted  in  the  same  slot, 
the  firing  lever  pivot  passing  through  the  spindle  key,  and  holding  it  in 
place.  On  the  rear  face  of  the  carrier  a  horizontal  groove  is  formed 
to  carry  the  rack.  The  slide  stop  is  screwed  into  the  top  surface  in 
the  upper  wall  of  the  rack  groove. 

The  operating  spool  is  placed  vertically  between  the  two  block- 
carrier  hinge  lugs.  The  hinge  pin  passes  vertically  through  the  center 
of  the  spool.  That  portion  of  the  hinge  pin  within  the  spool  is  squared, 
causing  the  spool  to  rotate  with  the  hinge  pin.  The  roller  groove  is 
cut  in  the  surface  of  the  spool.  The  translating  stud  is  formed  on  the 
surface  of  this  spool.  A  groove  is  cut  near  the  top  of  the  spool  for  the 
upper  latch  stud.  A  notch  is  cut  in  the  lower  edge  of  the  spool  to 
receive  the  end  of  the  latch  body  in  locking  together  the  spool  and 
carrier  while  the  block  is  swung  away  from  the  breech. 

The  operating  lever  fits  over  the  squared  end  of  the  hinge  pin,  and 
is  held  in  place  by  a  nut.  The  breech  mechanism  is  actuated  by  the 
operating  lever  acting  through  the  operating  spool.  When  the  breech 
is  closed,  the  operating  lever  lies  against  the  face  of  the  breech,  and 
is  held  in  this  position  by  the  lever  latch.  The  lever  latch  consists 
of  a  bolt  with  vertical  motion  in  a  housing,  and  pressed  downward  by 
the  lever-latch  spring.  The  housing  is  attached  to  the  breech  plate 
by  the  housing  screws.  Th6  downward  motion  of  the  latch  bolt  is 


ARMAMENT  145 

limited  by  a  stud  on  its  upper  end,  striking  the  ends  of  the  groove  in 
the  housing  in  which  the  stud  travels.  When  the  operating  lever 
is  against  the  breech,  the  head  of  the  bolt  enters  a  corresponding 
depression  in  the  top  surface  of  the  operating  lever,  holding  the  lever 
against  the  breech. 

The  rack  has  a  horizontal  motion  in  a  groove  in  the  rear  face  of  the 
block  carrier.  A  tooth  on  its  inner  end  engages  between  teeth  on  the 
stem  of  the  breech  block.  A  lug  on  the  outer  end  of  the  rack  works 
in  the  rotating  grooves  in  the  spool.  A  housing  is  formed  on  the  rear 
face  of  the  rack  for  the  rack  lock.  The  rack-lock  bolt  has  a  vertical 
motion  in  this  housing,  and  is  pressed  upward  by  a  spring.  A  handle 
is  screwed  into  the  lower  end  of  the  rack-lock  bolt.  The  upper  motion 
of  the  bolt  is  limited  by  a  shoulder  on  the  handle  striking  the  housing. 
The  upper  end  of  the  bolt  enters  a  slot  in  the  side  of  the  firing  mechan- 
ism, causing  the  slide  to  move  horizontally  with  the  rack.  By  pulling 
down  the  handle  the  bolt  is  withdrawn  from  the  notch  in  the  slide, 
allowing  the  slide  to  operate  independently  of  the  rack. 

The  latch  is  housed  in  a  notch  cut  through  the  lower  hinge  lug  of 
the  block  carrier,  and  held  in  place  by  the  latch  retainer.  A  stud  on 
the  upper  end  of  the  latch  rides  in  a  groove  cut  in  the  operating  spool, 
and  actuates  the  slide.  A  similar  stud  rotates  in  the  groove  cut  in  the 
lower  hinge  plate  lug.  When  the  block  carrier  is  against  the  breech, 
the  lower  stud  rests  in  a  vertical  portion  of  the  groove  of  the  hinge-lug 
pallet,  locking  the  carrier  in  position  during  rotation  and  translation 
of  the  block.  In  opening  the  breech,  when  the  translation  of  the  block 
is  complete,  the  latch  is  elevated  by  the  upper  stud,  causing  the  lower 
stud  to  rise  onto  the  vertical  groove  and  free  the  carrier  from  the  face 
of  the  breech.  At  the  same  time  the  upper  end  of  the  body  of  the  latch 
enters  a  notch  cut  in  the  operating  spool,  locking  the  spool  and  block 
carrier  together  while  the  block  is  swung  away  from  the  breech.  The 
action  of  the  latch  in  closing  the  breech  is  the  reverse  of  that  in  opening. 
The  latch  retainer  consists  of  a  block  of  steel  provided  with  a  ring 
handle  and  a  spring  catch.  It  is  inserted  in  the  latch  slot  in  the  hinge 
lug,  and  holds  the  studs  of  the  latch  in  their  grooves.  It  is  prevented 
from  dropping  out  of  the  slide  by  the  latch-retainer  spring. 

The  principal  parts  of  the  obturator  are  the  mushroom  head, 
spindle,  front  and  rear  exterior  split  rings,  interior  split  ring,  pad, 
filling-in  disk,  and  spindle  spring.  They  operate  in  a  manner  similar 
to  those  described  for  other  breech  mechanism. 

The  loading  tray  provided  remains  in  the  breech  recess  at  all  times. 
The  center  section  of  the  tray  is  cut  away  to  a  width  equal  to  one 


146  THE  SERVICE  OF  COAST  ARTILLERY 

of  the  sectors  of  the  breechblock,  leaving  a  solid  section  of  the  same 
width  on  each  side.  A  lip  is  formed  on  the  front  edge  and  one  on  the 
rear  edge  of  the  tray,  extending  downward.  These  lips  rest  in  annular 
grooves  in  the  breech  recess,  holding  the  tray  in  place  when  the  breech 
is  opened,  and  guiding  the  tray  during  its  rotation  with  the  breech- 
block. When  the  breech  is  open,  the  solid  sections  of  the  tray  cover 
the  two  lower  threaded  sectors  of  the  breech  recess.  The  tray  is 
prevented  from  being  displaced  laterally  by  a  shoulder  in  the  rear 
groove  011  the  right  side  and  by  the  loading-tray  latch  on  the  left  side. 
The  loading-tray  latch  consists  of  a  bolt  with  radial  motion  in  a  hole 
bored  through  the  gun,  and  pressed  inward  by  a  spring.  When  the 
breech  is  closed,  the  lower  threaded  sector  of  the  block  enters  the  solid 
sector  of  the  tray.  At  the  same  time,  the  block  bearing  against  the 
inner  end  of  the  tray-latch  bolt  forces  it  outward  and  frees  the  tray. 
During  the  rotation,  the  threaded  sector  of  the  block  working  in  the 
slotted  sector  of  the  tray  carries  the  tray  upward  to  the  left,  uncovering 
the  two  lower  threaded  sectors  of  the  breech  recess  to  permit  their 
engagement  into  their  corresponding  threaded  sectors  of  the  block. 

To  Open  the  Breech. — Grasp  the  handle  of  the  operating  lever, 
and  carry  it  to  the  right.  The  roller  causes  the  block  to  rotate  until 
the  rack  tooth  engages  the  teeth  on  the  block  stem.  The  remaining 
operations  are  the  reverse  of  those  described  in  closing  the  breech. 

To  Close  the  Breech. — Grasp  the  handle  of  the  operating  lever,  and 
carry  it  to  the  left  until  the  lever  latch  engages.  The  operating  spool 
turns  with  the  lever.  During  the  first  part  of  this  motion,  the  latch 
body  is  entered  in  its  notch  in  the  spool,  causing  the  block  carrier  to 
swing  with  the  spool  until  the  carrier  strikes  the  breech.  At  this 
time  the  latch  body  drops  out  of  its  notch  in  the  spool,  freeing  the 
spool  from  the  carrier.  The  downward  motion  of  the  latch  causes  the 
lower  latch  stud  to  enter  the  vertical  portion  of  the  groove  in  the  hinge- 
lock  bolt,  locking  the  carrier  against  the  breech.  As  the  spool  con- 
tinues to  rotate,  the  translating  stud  enters  the  translating  groove 
and  the  block  is  forced  forward  into  the  breech  recess.  At  the  end 
of  the  translation,  the  translating  stud  leaves  the  translating  groove, 
freeing  the  spool  for  further  rotation.  The  rack  stud  now  enters  the 
rotating  groove  and  the  rack  is  forced  to  the  left,  acting  through  the  teeth 
to  rotate  the  block  to  the  right.  Before  the  rotation  of  the  block  is 
complete,  the  racking  tooth  passes  beyond  the  teeth  on  the  stem  of 
the  block,  the  edge  of  the  left  tooth  of  the  stem  being  faced  off  for 
this  purpose.  The  roller,  actuated  by  the  cam  shaped  roller  groove, 
then  completes  the  rotation  of  the  block.  The  lower  part  of  the  roller 


ARMAMENT  147 

groove  is  so  shaped  that  the  roller  acts  as  a  stop  to  prevent  the  block 
from  rotating  under  firing  pressure. 

To  Remove  and  Dismount  Breech  Mechanism. — Open  the  breech, 
withdraw  the  latch  retainer  and  remove  the  latch.  The  breechblock 
is  now  free  to  be  translated  and  rotated  as  if  it  were  in  the  breech 
recess.  Hold  the  block  carrier  and  rotate  the  operating  lever  until 
translation  of  the  block  is  completed.  Remove  the  firing  lever  pivot 
pin  and  pivot.  Lift  the  firing  lever  out  of  its  slot  in  the  block  carrier. 
Lift  the  spindle  key  out  of  its  slot  in  the  block  carrier.  If  the  spindle 
key  seems  to  stick,  move  the  operating  lever  slightly  to  and  fro  until 
the  key  is  free. 

Continue  the  rotation  of  the  operating  lever  until  rotation  of  the 
block  is  completed.  Detach  firing  cable  from  the  firing-cable  bracket. 
Support  the  housing  of  the  firing  mechanism,  and  with  the  wrench 
provided  for  the  purpose  rotate  the  mushroom  head  to  the  left  until 
the  housing  is  free  from  the  spindle,  when  the  housing  may  be  with- 
drawn to  the  rear  by  holding  down  the  rack-lock  bolt. 

Remove  the  spindle  from  the  block  and  remove  the  spindle  spring. 
The  operating  lever  should  now  be  rotated  a  short  distance  farther. 
This  causes  the  teeth  on  the  end  of  the  stem  to  enter  the  groove  pro- 
vided for  them  in  the  hub  of  the  carrier.  The  stem  of  the  block  may  now 
be  removed  from  the  carrier.  Slide  the  rack  to  the  left  out  of  its  groove. 
Remove  the  hinge-pin  nut  and  take  off  the  operating  lever.  Support 
the  block  carrier  and  drive  out  the  hinge  pin,  using  a  copper  drift. 
The  block  carrier  and  operating  spool  are  now  free  to  be  removed. 

To  remove  the  loading  tray,  press  down  on  the  tray-latch  bolt  and 
lift  the  tray  from  its  place. 

To  dismount  the  lever  latch,  force  the  latch  bolt  upward  until  the 
stud  is  free  of  its  groove.  Turn  the  bolt  180  degrees  until  the  stud 
points  to  the  left,  when  the  bolt  may  be  lowered  out  of  the  housing, 
the  stud  passing  through  a  groove  cut  in  the  housing  for  this 
purpose. 

To  Assemble  the  Breech  Mechanism. — Place  the  hinge-lug  bushing 
in  its  seat  so  that  one  of  the  diagonals  of  its  rectangular  interior  will 
be  perpendicular  to  the  face  of  the  breech.  Place  the  carrier  bushing  in 
its  seat  so  that  one  of  the  diagonals  of  its  rectangular  interior  will  lie 
in  the  plane  of  the  carrier.  Support  the  carrier  so  that  its  plane  is 
perpendicular  to  the  face  of  the  breech,  placing  its  lugs  in  position  to 
receive  the  hinge  pin.  Place  the  spool  between  the  lugs  of  the  carrier, 
and  turn  so  that  the  circular  lower  end  of  the  roller  groove  faces  the 
body  of  the  carrier.  Insert  the  hinge  pin  carefully,  using  no  force 


148  THE  SERVICE  OF  COAST  ARTILLERY 

unless  positive  that  the  rectangular  holes  in  the  spool,  hinge-lug 
bushing,  and  carrier  bushing  are  in  line. 

Place  the  operating  lever  on  the  hinge  pin  so  that  the  lever  lies  in 
the  plane  of  the  carrier  and  screw  on  the  hinge-pin  nut.  Rotate  the 
operating  lever  slightly  to  the  left  and  enter  the  stem  of  the  breech- 
block in  the  carrier  until  the  roller  enters  the  roller  groove.  Place 
the  rack  in  its  groove.  Press  the  block  toward  the  carrier,  at  the 
same  time  rotating  the  operating  handle  slightly  to  the  right  and 
entering  the  stud  of  the  rack  in  the  rotating  groove. 

Assemble  the  obturator  and  firing-mechanism  housing,  being  careful 
to  stop  the  rotation  of  the  mushroom  head  when  the  ejector  drops 
into  its  slot  in  the  spindle.  The  slide  must  be  assembled  in  the  housing 
before  the  housing  is  assembled  to  the  spindle.  Rotate  the  operating 
lever  until  rotation  of  the  block  is  completed. 

Assemble  the  spindle  key  and  firing  lever;  rotate  the  operating 
lever  until  translation  of  the  block  is  completed.  Insert  the  latch. 
On  one  end  of  the  latch  the  dovetail  projection  from  the  latch  retainer 
is  cut  away.  This  is  the  lower  end  of  the  latch.  Assemble  the  latch 
retainer. 

6-lNCH  RAPID-FIRE  GUN,  MODEL  OF  1905 

This  is  the  latest  type  of  6-inch  rifle  and  differs  in  construction 
from  the  model  of  1903  only  in  the  following  points: 

1  A  hoop,  which  extends  forward  of  the  trunnion  hoop  and  is  locked 
to  the  D  hoop  by  a  locking  hoop.  Form  of  powder  chamber  cylindrical. 

5-lNCH  RAPID-FIRE  GUN,  MODEL  OF  1897 

This  gun  follows  the  general  method  of  built-up  forged-steel  con- 
struction. It  consists  of  a  tube,  jacket,  locking  hoop,  breech  mechan- 
ism and  associate  parts. 

The  tube  forms  the  bore  and  powder  chamber,  and  is  reinforced 
by  the  jacket  and  locking  hoop.  The  method  of  assembling  is  similar 
to  that  of  larger  calibers.  The  object  of  the  locking  hoop  is  to  lock 
the  tube  and  jacket  in  place,  thus  preventing  any  backward  movement 
of  the  jacket.  It  has  a  shoulder  on  its  inner  surface  which  bears  against 
the  front  face  of  a  corresponding  shoulder  on  the  tube  just  in  front 
of  the  forward  end  of  the  jacket.  The  breech  end  of  the  jacket  projects 
beyond  the  rear  face  of  the  tube  and  forms  a  recess  which  is  threaded 
with  a  V-shape  thread  with  rounded  top  and  bottom,  slotted  for  the 
interrupted  screw  mechanism;  this  forms  the  seat  for  the  breechblock. 


ARMAMENT  149 

The  powder  chamber  is  cylindrical  and  has  the  breech  end  slightly 
enlarged  to  form  a  conical  gas-check  seat  which  permits  the  easy 
insertion  and  withdrawal  of  the  gas-checking  device.  There  is  also  a 
conical  slope  and  forcing  slope.  The  twist  of  rifling  is  increasing  from 
one  turn  in  50  calibers  to  one  in  25  calibers;  there  are  30  grooves  in 
the  bore. 

The  breech  mechanism  consists  of  the  breechblock,  gear  segment, 
block  carrier,  lever,  pinion,  latch,  obturator,  and  associate  parts. 
The  breechblock  is  cylindrical  with  an  axial  hole  for  the  reception  of 
the  spindle  and  washer. 

The  front  part  of  the  block  for  a  short  distance  is  reduced  in 
diameter;  this  allows  a  space  in  the  breech  recess  of  the  gun  in  which 
fouling  may  collect  without  interruption  to  the  working  of  the  block. 

The  outer  surface  of  the  block  has  cut  upon  it  a  V-shaped  screw 
thread  with  rounded  top  and  bottom;  this  screw  thread  is  divided 
into  8  equal  parts  and  the  threads  are  cut  from  alternate  sectors. 
The  sectors  from  which  the  threads  are  cut  are  called  the  slotted 
sectors;  while  those  alternating  with  them  are  called  the  threaded 
sectors.  The  sectors  from  which  the  threads  are  cut  permit  the 
entry  of  the  block  past  the  corresponding  threaded  sectors  in  the 
breech  recess.  By  revolving  the  block  through  an  angle  of  45  degrees 
with  its  longitudinal  axis,  the  threaded  sectors  of  the  block  are  engaged 
with  the  threaded  sectors  of  the  recess.  In  order  to  provide  sufficient 
clearance  for  the  breechblock  to  swing  away  from  the  piece  certain 
parts  of  the  threaded  and  slotted  sectors  are  cut  away. 

The  rear  end  of  the  block  is  turned  down  to  a  smaller  diameter, 
and  the  cylindrical  surface  thus  formed  is  prolonged  into  the  block 
and  increased  in  length  by  means  of  an  annular  cut  in  the  rear  face  of 
the  block.  This  cylindrical  surface  is  called  the  guide  cylinder;  the 
annular  groove  being  called  the  guide  groove  of  the  block.  That 
portion  of  the  rear  face  of  the  block  which  lies  outside  of  the  guide 
groove  is  called  the  stop  flange.  When  the  block  is  withdrawn  the 
stop  flange  strikes  the  bottom  of  the  stop  groove  in  the  block  carrier 
and  limits  the  rearward  motion  of  the  block.  The  block  is  guided 
and  supported  in  its  motions  of  rotation  and  translation  by  the  guide 
cylinder.  The  block  is  provided  with  four  oil  holes  drilled  radially 
from  the  exterior  of  the  block  to  'he  bottom  of  the  guide  groove;  this 
is  to  facilitate  oiling  of  the  bearing  surfaces  as  well  as  acting  as  air 
vents. 

A  locking  recess  is  cut  in  the  surface  of  the  guide  cylinder  gradually 
increasing  in  depth  from  rear  to  front;  when  the  block  is  withdrawn 


150  THE  SERVICE  OF  COAST  ARTILLERY 

the  inner  end  of  the  latch  bolt  drops  into  the  locking  recess  and  locks 
the  block  to  the  carrier. 

The  gear  segment  is  attached  to  the  rear  end  of  the  breechblock 
and  consists  essentially  of  a  segment  of  beveled  gear  and  a  short  rack, 
which  mesh  with  a  pinion  pivoted  on  the  block  carrier  and  actuated 
by  the  lever.  Part  of  the  periphery  of  the  pinion  is  cut  into  a  beveled 
gear  and  another  part  into  a  pinion,  meshing  \vith  the  corresponding 
parts  of  the  gear  segment.  The  beveled  gear  part  rotates*  the  block 
and  the  rack  and  pinion  parts  translate.  The  termination  of  the 
motion  of  rotation  in  opening  the  breech  brings  the  rack  and  pinion 
into  the  proper  position  to  withdraw  the  block,  and  the  end  of  the  motion 
of  translation  in  closing  the  breech  brings  the  beveled  gear  segments 
into  mesh  and  thus  rotated. 

The  block  carrier  is  a  steel  casting  provided  by  means  of  a  pivoted 
pin  to  a  hinged  plate  attached  to  the  j  acket  on  the  right  side  of  the 
breech;  its  function  is  to  support  the  block  in  its  various  movements. 

For  actuating  the  pinion,  a  lever  is  fitted  on  a  squared  extension  of 
the  lug;  the  free  end  of  the  lever  terminates  in  a  vertical  handle. 

The  latch  consists  of  the  latch  bolt,  latch  spring,  latch  lever  and 
latch-lever  pivot;  which  are  mounted  in  the  block  carrier;  and  the 
latch-bolt  seat  and  tripping  stud,  which  are  secured  to  the  breech  face 
of  the  piece  by  screws.  The  function  of  the  latch  is  to  lock  the  block 
to  the  carrier.  When  the  block  is  swung  away  from  the  breech,  the  inner 
end  of  the  latch  bolt  rests  in  the  locking  recess  and  locks  the  bolt  to 
the  carrier.  In  this  position  the  upper  end  of  the  latch  lever,  against 
which  the  spring  bears,  projects  slightly  beyond  the  exterior  surface  of 
the  carrier.  When  the  breech  is  closed,  just  before  the  carrier  comes 
in  contact  with  the  breech  face  of  the  piece,  this  projecting  part  of  the 
lever  strikes  the  beveled  surface  of  the  tripping  stud  and  is  forced 
toward  the  axis  of  the  block.  The  lever  lifts  the  latch  bolt  from  the 
locking  recess  and  the  block  is  then  free  to  be  translated  through  the 
block  carrier. 

A  summary  of  the  complete  action  of  the  latch  may  be  stated  as 
follows:  With  the  breech  closed,  the  outer  end  of  the  latch  bolt  rests 
in  the  latch-bolt  seat,  locking  the  block  carrier  to  the  breech  face  of  the 
gun;  the  inner  end  of  the  latch  bolt  bears  against  the  guide  cylinder 
of  the  block,  and  at  the  end  of  the  motion  of  rotation  of  the  block 
in  opening  the  breech,  rests  in  line  with  the  end  of  the  latch  groove. 
When  the  block  is  withdrawn  the  bolt  rides  down  the  inclined  bottom 
of  the  latch  groove  and  its  outer  end  is  withdrawn  from  the  latch-bolt 
seat,  freeing  the  block  carrier  from  the  breech  of  the  piece.  At  the  end 


*>  OF  THE 

UNIVERSIT 


ARMAMENT  151 

of  the  motion  of  withdrawal  the  inner  end  of  the  latch  bolt  enters 
the  locking  recess  in  the  breechblock.  When  the  block  carrier  is 
swung  away  from  the  piece  the  end  of  the  latch  lever  clears  the  tripping 
stud  so  that  the  full  force  of  the  latch  spring  comes  into  play,  and  the 
latch  bolt  is  forced  to  the  bottom  of  the  locking  recess,  thus  securely 
locking  the  block  to  the  carrier.  When  the  breech  is  closed  the  action 
of  the  latch  is  the  reverse  of  that  just  given.  With  the  breech  open, 
the  block  is  locked  to  the  carrier.  When  the  carrier  is  swung  against 
the  breech  face  of  the  piece,  the  tripping  stud,  by  means  of  the  lever, 
raises  the  latch  bolt  far  enough  from  the  bottom  of  the  latch-groove 
locking  recess  for  the  end  of  the  bolt  to  ride  on  the  inclined  bottom 
of  the  groove  as  the  block  is  moved  forward  through  the  block  carrier. 
As  the  bolt  rides  up  the  inclined  bottom  of  the  latch  groove  its  outer 
end  enters  the  latch-bolt  seat  and  locks  the  block  carrier  to  the  breech 
face  of  the  piece. 

The  obturator  consists  of  the  spindle,  front  and  rear  exterior  split 
rings,  interior  split  ring,  pad,  filling-in  disk,  spindle  nut,  and  spindle-ball 
wajsher.  Its  purpose  is  to  prevent  the  escape  of  gas  from  the  powder 
•chamber  to  the  rear  during  firing,  and  to  transmit  to  the  breechblock 
the  stress  of  firing  resulting  from  the  pressure  of  the  gases  upon  the 
bottom  of  the  bore. 

The  gas-check  pad  is  a  disk  of  asbestos  and  tallow,  compressed  under 
heavy  pressure  and  covered  with  canvas.  It  forms  a  yielding  medium 
for  the  transmission  of  pressure  to  the  block,  and  under  the  pressure  of 
firing  the  plastic  nature  of  the  pad  causes  it  to  press  outward  toward 
the  gas-check  seat  and  inward  against  the  spindle,  forcing  the  split 
rings  firmly  against  their  seats  and  completely  stopping  the  passage  of 
gas. 

The  spindle-ball  washer  consists  of  two  steel  rings  with  a  groove 
cut  in  one  face  of  each  ring  to  form  a  pocket  for  twenty  hardened- 
steel  balls.  The  washer  is  interposed  between  the  spindle  nut  and 
the  breechblock  for  the  purpose  of  reducing  the  friction  between  them 
when  the  block  is  rotated. 

To  Open  the  Breech. — When  the  block  is  closed  the  lever  lies 
parallel  to  the  face  of  the  breech,  with  the  handle  to  the  left.  Moving 
the  handle  to  the  rear  and  right  rotates  the  block  through  an  angle  of 
45  degrees  and  disengages  the  threaded  sectors  on  the  block  from 
those  in  the  breech  recess.  The  further  movement  of  the  handle 
draws  the  block  to  the  rear  until  the  stop  flange  strikes  the  bottom 
of  the  stop  groove  and  the  head  of  the  latch  bolt  comes  opposite  the 
locking  recess.  This  movement  of  the  block  to  the  rear  frees  the 


152  THE  SERVICE  OF  COAST  ARTILLERY 

gas  check  from  its  seat  in  the  gun  sufficiently  to  enable  the  block, 
supported  by  the  carrier,  to  be  swung  out  of  the  recess  and  to  one  side 
of  the  piece  about  the  block-carrier  hinge  pin  as  a  center.  At  the  end 
of  the  motion  of  withdrawal  the  outer  end  of  the  latch  bolt  is  with- 
drawn from  its  seat,  freeing  the  block  carrier  from  the  breech  face  of 
the  gun  so  that  a  further  motion  of  the  lever  handle  to  the  right  swings 
the  block  carrier  and  block  away  from  the  piece.  During  this  move- 
ment the  latch  bolt  has  locked  the  block  to  the  block  carrier. 

To  Close  the  Breech. — The  lever  handle  is  moved  to  the  left  as 
far  as  it  will  go.  The  action  of  the  various  parts  of  the  mechanism 
in  closing  the  breech  is  the  reverse  of  their  action  in  opening  it. 

To  Remove,  Dismount  and  Assemble  Breech  Mechanism. — -See 
method  under  6-lNCH  R.-F.  GUN,  MODEL  OF  1897  Mi. 

Total  length  231.6  inches;  weight  7,583  pounds;  length  of  bore 
45  calibers;  weight  of  projectile  58  pounds;  weight  of  propelling 
charge,  nitro-cellulose  powder,  16^  pounds;  weight  of  bursting  charge, 
A. P.  shell  2.3  pounds  of  gun  cotton;  C.I.  shell  2  pounds  of  rifle  powder; 
shrapnel  .75  pounds  of  rifle  powder. 

Muzzle  velocity  2,600  foot-seconds.  Muzzle  energy  2,721  foot- 
tons.  Maximum  pressure  38,000  pounds  per  square  inch.  Maximum 
elevation  permitted  by  carriage  15  degrees;  corresponding  range 
10,431  yards.  Penetration  in  Krupp  cemented  armor,  at  5,000  yards, 
2.36  inches. 

5-lNCH  RAPID-FIRE  GUN,  MODEL  OF  1900 

This  rifle  is  similar  in  construction  to  the  model  of  1897,  except 
that  it  has  2  A  hoops,  2  C  hoops,  and  1  D  hoop.  The  powder  chamber 
is  cylindro-conical. 

The  breech  mechanism  in  this  model  has  the  guide  groove  tapered 
instead  of  cylindrical;  there  is  no  spindle  key;  the  rotation  of  the 
block  is  limited  by  a  breechblock  stop;  there  is  an  automatic  loading 
tray  of  bronze. 

Total  length  258.5  inches;  weight  11,120  pounds;  length  of  bore 
50  calibers;  weight  of  projectile.  58  pounds;  weight  of  propelling 
charge,  nitro-cellulose  powder,  26  pounds. 

Muzzle  velocity  2,600  foot-seconds.  Muzzle  energy  3,623  foot- 
tons.  Maximum  pressure  36,000  pounds  per  square  inch.  Maximum 
elevation  permitted  by  the  carriage  15  degrees;  corresponding  range 
11,791  yards.  Penetration  in  Krupp  cemented  armor,  at  5,000  yards, 
2.89  inches. 


ARMAMENT  153 

4.72-lNCH  QUICK-FIRING  ARMSTRONG  GUN,  50  CALIBERS 

(See  Plate  XV) 

This  rifle  follows  the  general  method  of  built-up  forged  steel  con- 
struction. It  consists  of  a  tube,  jacket,  and  what  in  the  service  would 
be  termed  2  C  hoops,  and  1  A  hoop.  In  order  to  obtain  great  rapidity 
of  fire  a  special  mount  is  provided.  The  gun  has  no  trunnions.  It 
is  carried  in  a  cradle  which  encircles  it  and  in  which  it  slides  when 
recoiling;  this  cradle  is  provided  with  trunnions  upon  which  the  gun 
and  cradle  are  balanced.  The  powder  chamber  is  conical.  The 
breech  is  surrounded  by  a  breech  ring  which  has  a  projecting  arm  on 
it  for  connecting  the  gun  with  the  recoil  cylinder,  which  forms  part 
of  the  cradle.  The  mechanism  for  closing  the  breech  is  of  the  inter- 
rupted screw  type,  so  arranged  that  it  can  be  quickly  opened  or 
closed  by  a  single  movement. 

The  breech  mechanism  is  practically  the  same  as  6-inch  Armstrong 
rifle,  except  that  it  is  smaller  in  dimension,  and  is  of  the  screw  form 
in  two  steps,  the  front  step  being  tapered  and  of  less  diameter  than 
the  rear.  Both  steps  have  three  portions  of  their  threads  removed, 
each  one-sixth  of  a  turn;  the  threads  on  one  set  standing  opposite 
to  the  blank  spaces  on  the  other;  this  is  done  in  order  to  distribute 
the  strain  all  around  the  circumference  of  the  breech  screw.  The 
interior  of  the  gun  at  the  breech  is  prepared  in  a  similar  manner  and 
admits  of  the  breech  screw  being  swung  into  place  and  locked  by  a 
simple  mechanism  provided. 

The  breech  screw  is  supported  by  a  carrier  on  which  it  is  free  to 
revolve  through  an  angle  of  60  degrees;  the  carrier  is  hinged  to  the 
right  side  of  the  breech  ring  so  that  the  screw  can  swing  clear  of 
the  breech  recess  for  loading.  A  stop  bolt  is  provided  for  securing 
the  carrier  and  the  block  together.  A  projecting  pin  is  screwed  into 
the  rear  face  of  the  breechblock,  and  enters  the  traversing  bush  in 
the  sliding  block.  This  block  slides  in  a  seat  in  the  carrier  and  is 
connected  with  the  hand-locking  lever  by  the  link.  The  block  is 
prevented  from  turning  on  the  carrier  when  open  by  a  spring  catch 
which  engages  a  notch  in  the  block  as  it  is  withdrawn  from  the 
gun.  When  the  breech  is  closed  the  catch  comes  in  contact  with  the 
face  of  the  gun,  releases  the  block  and  allows  it  to  be  screwed 
home. 

A  safety  gear  consisting  of  a  pawl  and  spindle,  the  pawl  of  which 
engages  a  lip  on  the  striker  and  prevents  the  latter  from  touching 


154  THE  SERVICE  OF  COAST  ARTILLERY 

the  primer  until  the  block  is  completely  closed  and  locked,  makes  it 
impossible  to  fire  the  gun  until  everything  is  safe. 

To  Open  the  Breech. — The  breechblock  is  unscrewed  and  withdrawn 
from  the  gun  by  a  single  horizontal  movement  of  the  hand-locking 
lever,  which  is  pivoted  on  the  right  side.  A  reverse  movement  com- 
pletely closes  and  locks  the  block. 

Total  length  236  inches;  weight  6,160  pounds;  length  of  bore  49 
calibers.  The  bore  has  26  grooves,  twist  of  rifling  1  turn  in  600 
calibers  to  one  turn  in  30  calibers.  Weight  of  projectile  45  pounds; 
weight  of  propelling  charge,  nitro-cellulose  powder,  8.2  pounds;  cordite 
10.5  pounds.  Weight  of  bursting  charge,  strong  head  steel  shell,  2 
pounds  of  high  explosive;  steel  shell  4.5  pounds  of  high  explosive; 
cast  iron  shell  1.2  pounds  of  rifle  powder;  shrapnel  .125  pound  of 
rifle  powder. 

Muzzle  velocity  2,600  foot-seconds.  Muzzle  energy  2,111  foot-tons. 
Maximum  pressure  34,000  pounds  per  square  inch.  Maximum  range 
11,211  yards. 

Penetration  in  Krupp  cemented  armor  with  uncapped  projectile, 
at  5,000  yards,  1.3  inches. 

4.72-lNCH  QUICK-FIRING  ARMSTRONG  GUN,  45  CALIBERS 
This  rifle  is  similar  in  construction  to  the  50-caliber  model  of  the 
same  make,  with  the  following  exceptions: 

Total  length  212.6  inches;  weight  5,958  pounds;  length  of  bore 
44  calibers.  Number  of  grooves  in  bore  26;  twist  of  rifling  increasing 
from  0  to  1  in  30  calibers.  Weight  of  projectile  45  pounds;  weight  of 
propelling  charge,  nitro-cellulose  powder,  8.2  pounds,  cordite  10.5  pounds. 
Muzzle  velocity  2,570  foot-seconds.  Muzzle  energy  2,063  foot-tons. 
Maximum  range  11,110  yards.  Penetration  in  Krupp  cemented  armor 
with  uncapped  projectile,  at  5,000  yards,  1.27  inches. 

4.72-lNCH  QUICK-FIRING  ARMSTRONG  GUN,  40  CALIBERS 
This  rifle  is  similar  in  construction  to  the  50-caliber  model  of  the 
same  make,  with  the  following  exceptions: 

Total  length  194.1  inches;  weight  4,648  pounds;  length  of  bore 
40  calibers.  Number  of  grooves  in  bore  22;  twist  of  rifling  from  one 
turn  in  100  calibers  to  one  turn  in  34  calibers.  Weight  of  propelling- 
charge,  nitro-cellulose  powder,  7.5  pounds;  cordite  5.5  pounds. 

Muzzle  velocity  2,150  foot-seconds.  Muzzle  energy  1,444  foot- 
tons.  Maximum  range  9,669  yards.  Penetration  in  Krupp  cemented 
armor  with  uncapped  projectile,  at  5,000  yards,  1.3  inches/ 


OF   THE 

UNIVERSITY 

OF 


ARMAMENT  155 

4-IxcH  RAPID-FIRE  DRIGGS-SCHROEDER  (ir.\ 

This  rifle  follows  the  general  method  of  built-up  forged-steel  con- 
struction. Manufactured  by  the  American  Ordnance  Company. 

Total  length  166.5  inches;  weight  3,613  pounds;  length  of  bore 
40  calibers;  twist  of  rifling  0  to  1  in  25  calibers;  weight  of  projectile 
33  pounds;  weight  of  propelling  charge,  nitro-cellulose  powder,  7.5 
pounds;  weight  of  bursting  charge  approximately  4.5  pounds  of  high 
explosive  for  shell,  2  pounds  for  strong-headed  shell. 

Muzzle  velocity  2,300  foot-seconds.  Muzzle  energy  1,212  foot- 
tons.  Maximum  pressure  34,000  pounds  per  square  inch.  Maximum 
range  8,864  yards. 

SECONDARY  ARMAMENT 
(See    Plate    XVI) 

3-IxcH  (15-POUNDER)   R.    F.    GUN,  DRIGGS-SEABURY  MODEL  OF  1898 

This  rifle  follows  the  general  method  of  built-up  forged-steel 
construction.  Manufactured  by  the  Driggs-Seabury  Company.  It 
consists  of  a  tube,  jacket,  and  breech  bushing. 

The  breech  mechanism  (Figs.  14  and  15)  consists  of  the  block,  the 
carrier  plate,  the  carrier-plate  ring  and  its  screws,  the  block-locking 
spring,  the  operating  lever  and  pin,  the  lever-catch  plunger,  spring  and 
cotter  pin,  the  firing  pin  and  spring,  the  sear,  the  sear  spring,  the 
extractor,  and  the  hinge  pin. 

The  principal  parts  of  the  breechblock  are  three  threaded  sectors, 
three  slotted  sectors,  the  thread  for  the  carrier  ring,  the  operating- 
lever  slots,  the  recess  for  the  firing  pin,  the  rotating  stop,  and  the  seat 
for  the  block-locking  spring. 

The  thread  is  V-shaped,  rounded  at  top  and  bottom,  and  for  about 
f  inch  in  rear  is  continuous;  the  remainder  is  divided  into  six  equal 
sectors,  three  threaded  and  three  slotted.  The  continuous  thread 
engages  in  that  of  the  carrier-plate  ring,  and  the  threaded  sectors 
engage  those  of  the  breech  recess.  The  slotted  sectors  of  both  blocks 
and  recess  are  cut  away  sufficiently  to  permit  the  block  to  enter  the 
recess  when  swung  about  the  hinge  pin.  The  slot  for  the  block-locking 
spring  is  so  placed  that  when  the  threads  of  the  block  are  disengaged 
from  those  of  the  breech  recess  the  spring  enters  the  slot  of  the  locking- 
block  and  carrier  plate  together. 


156 


THE  SERVICE  OF  COAST  ARTILLERY 


Extractor 


Hinge  Pin. 
\      \  •— \ — Carrier  Plate. 


FIG.  14. 


Carrier  P/ng. 
Block. 


Block-Jock  in 
Bolt  *  Spring 


FIG.  15. 


ARMAMENT  157 

The  carrier  plate  has  a  lug,  at  right  angles  to  its  face,  through  which 
passes  the  hinge  pin,  and  which  is  so  shaped  as  to  operate  the  extractor 
in  opening  the  breech.  Two  lugs,  projecting  from  the  rear  face,  carry 
the  operating-lever  pin,  and  the  lower  one  also  furnishes  the  seat  for 
the  lever-catch  mechanism.  A  lug  on  the  front  face  is  bored  out  to 
receive  the  firing  pin  and  its  spring,  and  is  assembled  into  the  cavity 
of  the  block.  The  carrier  plate  is  bored  from  the  right-hand  side  to 
receive  the  sear  and  its  spring.  The  rotating  stop  groove  is  annular, 
ends  in  a  shoulder,  and  is  cut  in  the  front  face  of  the  carrier  plate. 

A  slot  for  the  operating  lever  is  cut  through  the  carrier  plate,  and 
another  for  the  cocking  toe  is  cut  partly  through.  The  front  face  of 
the  carrier  plate  is  counter-sunk  to  receive  the  carrier-plate  ring,  which 
is  assembled  to  it  by  means  of  two  screws,  the  holes  for  which  are 
centered  by  a  rib  on  the  carrier  plate  and  a  corresponding  groove  on 
the  carrier-plate  ring. 

The  carrier-plate  ring  is  threaded  on  its  inner  surface  to  receive 
the  breechblock,  and  is  assembled  to  the  carrier  plate  by  two  screws. 
A  groove  in  the  front  face  seats  the  block-locking  spring,  has  a  rib 
part  of  its  length,  and  ends  at  the  interior  of  the  ring  in  a  recess  for 
assembling  the  spring  and  for  the  seat  of  its  locking  lug.  The  threads 
are  slightly  cut  away  in  two  places  to  make  a  clearance  for  the  operating- 
lever. 

The  block-locking  spring  is  assembled  to  the  carrier-plate  ring  by 
means  of  a  dovetail  groove.  At  the  lower  end  of  the  spring  there  is 
a  lug  that  locks  the  block  to  the  ring  when  the  spring  is  not  compressed; 
when  it  is  compressed,  one  side  of  the  lug  on  the  spring  forms  a  contin- 
uous surface  with  the  thread  of  the  ring,  permitting  rotation  of  the 
block. 

For  all  guns  after  number  80  a  modified  form  of  block-locking  bolt 
and  spring  is  employed. 

The  locking  bolt  for  securing  the  block  to  the  carrier  in  the  open 
position  passes  through  the  carrier-plate  ring,  being  forced  forward 
by  its  spring.  When  in  the  forward  position  a  projection  on  the 
bolt  enters  a  recess  in  the  rear  face  of  the  block,  locking  it  to  the 
carrier.  When  the  carrier  is  closed  the  locking  bolt  is  forced  to  the  rear 
and  held  there,  its  front  end  being  in  contact  with  the  face  of  the  breech. 

The  operating  lever  is  assembled  to  lugs  on  the  rear  face  of  the 
carrier  plate  and  consists  of  the  lever  proper,  the  operating  knob, 
the  cocking  cam,  the  handle,  the  seat  for  the  pin,  and  the  seat  for  the 
lever-catch  plunger.  The  lever  passes  through  the  carrier  plate,  the 
knob  engaging  in  its  seat  in  the  block  and  forcing  it  to  rotate  when 


158  THE  SERVICE  OF  COAST  ARTILLERY 

the  lever  is  turned  about  its  pin.  The  cocking  cam  engages  a  lug  on 
the  firing  pin  and  is  so  shaped  that  in  opening  the  breech  the  pin  is 
retracted  until  caught  and  held  by  the  sear.  The  lever  projects  to 
the  front  sufficiently  to  form  a  locking  lug  that,  by  the  final  motion 
in  closing,  is  seated  in  a  groove  in  the  rear  face  of  the  block,  thus 
preventing  rotation  of  the  block  due  to  pressure  of  the  powder  gas. 
The  final  movement  of  the  lever  in  closing,  and  the  first  in  opening,  is 
perpendicular  to  the  face  of  the  plate,  the  pin  hole  being  elliptical  for 
the  purpose.  The  seat  for  the  lever-catch  plunger  is  on  the  under  side 
of  the  lever.  The  handle  makes  a  right  angle  with  the  lever  and  is 
vertical. 

The  lever-catch  plunger,  with  its  spring,  is  assembled  in  the  lower 
lever  lug  and  is  secured  in  place  by  the  cotter  pin  passing  through 
the  lower  end  of  the  plunger.  The  mechanism  prevents  rotation  of  the 
handle  during  counter  recoil. 

The  firing  pin  and  spring  are  assembled  in  their  seat  in  the  carrier 
plate,  the  pin,  when  released,  passing  through  an  aperture  in  the 
front  of  the  block.  The  pin  has,  at  the  rear  end,  a  cocking  lug  and 
a  notch  for  the  engagement  of  the  sear,  and  in  front  a  shoulder  for 
the  spring.  The  spring  is  coiled  around  the  pin  and  abuts  against 
the  shoulder  on  the  pin  in  front  and  the  carrier  plate  in  rear. 

The  sear  and  its  spring  are  assembled  to  the  carrier  plate  in  a  seat 
bored  parallel  to  the  right-hand  horizontal  radius.  The  sear  is  so  shaped 
at  its  inner  end  as  to  hold  the  firing  pin  in  its  retracted  position,  except 
when  rotated  upward.  The  outer  end  of  the  sear  terminates  in  a 
short  lever,  carrying  an  eye  for  the  lanyard;  near  this  eye  there  is  a 
seat  for  one  end  of  the  sear  spring,  the  other  end  of  which  is  secured 
in  the  carrier  plate,  the  tendency  of  the  spring  being  to  keep  the  sear 
rotated  downward. 

The  extractor  passes  through  a  slot  in  the  right  side  of  the  jacket 
into  the  breech  recess,  is  assembled  to  the  jacket  by  two  studs  fitting 
into  grooves,  and  is  operated  by  a  lug  on  the  carrier  plate,  so  shaped  as 
to  give  the  extractor  a  quick,  lateral  motion  for  the  purpose  of  throwing 
the  case  clear  of  the  breech.  The  hinge  pin  assembles  the  carrier 
plate  to  the  jacket. 

Action  of  Breech  Mechanism. — Immediately  after  the  gun  has  been 
fired  the  block  threads  engage  those  of  the  breech  recess,  the  operating- 
lever  is  against  the  carrier  plate,  the  locking  lug  on  the  lever  is  seated 
in  its  groove  in  the  block,  the  lever-catch  plunger  is  in  its  seat,  the  firing 
pin  is  forward  against  the  primer,  and  the  block-locking  spring  lug 
forms  a  part  of  the  carrier-ring  thread. 


ARMAMENT  159 

To  Open  the  Breech. — Rotate  the  handle  to  the  right  until  the 
carrier  comes  to  rest  against  the  jacket.  At  the  beginning  of  the 
movement  to  open  the  breech,  the  locking  lug  on  the  lever  is  with- 
drawn from  its  seat,  the  knob  causes  the  block  to  rotate  from  left  to 
right  until  the  threaded  sectors,  are  disengaged  from  those  of  the 
breech  recess,  the  stop  on  the  block  strikes  the  shoulder  of  its  seat 
when  this  disengagement  is  complete,  and  the  block  swings  clear  of  the 
breech  recess.  During  the  rotation  of  the  lever  the  cocking  cam 
retracts  the  firing  pin,  which  is  then  held  by  the  sear.  As  soon  as  the 
carrier  has  moved  far  enough  from  the  face  of  the  breech,  the  block- 
locking  spring  is  released  and  locks  the  block  to  the  ring. 

To  Close  the  Breech. — Rotate  the  handle  to  the  left  until  the  lever 
brings  up  against  the  carrier  plate.  The  block-locking  spring  is  com- 
pressed by  striking  the  breech,  and  then  the  action  of  the  mechanism 
is  that  of  opening,  reversed,  except  that  the  firing  pin  is  not  affected. 
For  drill  purposes  an.  empty  cartridge  case  should  be  inserted  in  the 
chamber,  ac  otherwise,  unless  care  is  taken  that  the  operating  lever 
is  left  firmly  against  the  breech  after  closing,  snapping  the  lock  is 
liable  to  break  the  firing  pin. 

To  Assemble  the  Breech  Mechanism. — Seat  the  extractor.  Put 
the  carrier  plate  in  position  and  insert  the  hinge  pin.  Put  the  lever- 
catch  plunger  spring  in  its  seat,  insert  the  plunger,  press  it  down,  and 
enter  the  cotter  pin.  Seat  the  block-locking  spring  in  the  carrier 
ring.  Place  the  carrier  ring  in  the  carrier  plate  and  insert  the  securing 
screws.  Close  the  carrier  plate  until  it  rests  against  the  breech  of 
the  gun.  Insert  the  sear  and  its  spring,  guiding  the  end  of  the  latter 
into  its  seat  in  the  carrier  plate.  Assemble  the  firing-pin  spring  to 
the  pin.  Swing  the  carrier  plate  away  from  the  breech,  seat  the  firing 
pin  in  the  stem  of  the  plate,  keeping  the  guide  rib  downward,  and 
compress  the  spring  until  the  pin  is  held  by  the  sear.  A  block  of 
wood  should  be  used  against  the  point  of  the  pin  in  compressing  the 
spring. 

Place  the  breechblock  on  the  stem  of  the  carrier  plate,  compress  the 
block-locking  spring,  and  rotate  the  block  to  the  left  until  the  stop 
comes  in  contact  with  the  shoulder  of  its  groove  in  the  carrier  plate. 
Release  the  block-locking  spring.  Place  the  operating  lever  in  position 
and  insert  the  lever  pin.  Close  the  breech. 

To  Dismount  the  Breech  Mechanism. — Reverse  the  operations  of 
assembling,  being  sure  that  the  firing  pin  is  cocked  before  beginning. 

The  other  parts  of  the  breech  mechanism,  except  the  extractor, 
may  be  first  assembled  to  the  carrier  plate  and  then  the  whole  assembled 


160  THE  SERVICE  OF  COAST  ARTILLERY 

to  the  gun;  dismounting  may  be  similarly  effected  by  first  removing 
the  mechanism  as  a  whole. 

Total  length  154.5  inches;  weight  1,782  pounds;  length  of  bore 
50  calibers.  The  bore  has  24  grooves;  twist  of  rifling  1  in  50  to  1  in  25 
calibers.  Weight  of  projectile,  shot,  shell,  or  shrapnel,  15  pounds; 
weight  of  propelling  charge,  nitro-cellulose  powder,  5  pounds. 

Muzzle  velocity  2,600  foot-seconds.  Muzzle  energy  703.8  foot- 
tons.  Maximum  pressure  34,000  pounds  per  square  inch.  Maximum 
elevation  permitted  by  carriage  12  degrees,  corresponding  range  7,849 
yards.  Penetration  in  Krupp  cemented  armor,  at  5,000  yards, 
uncapped  projectile,  .77  of  an  inch. 

3-lNCH    (15-POUNDER)    RAPID-FlRE    GUN,    MODEL    OF    1902 

(See  Plate  XVII) 

This  rifle  follows  the  general  method  of  built-up  forged-steel  con- 
struction. It  consists  of  a  tube,  jacket,  hoop,  breech  mechanism,  etc. 
The  tube  is  enveloped  by  a  jacket  and  hoop  for  a  distance  of  84  inches 
from  the  breech  end. 

The  breech  mechanism  consists  principally  of  the  block,  carrier  plate, 
latch,  carrier  hub,  operating  lever,  link  extractor  and  firing  mechanism. 

The  block  is  cylindrical  in  form,  4.4  inches  long,  5.7  inches  in  exterior 
diameter,  except  at  the  rear  end,  where  there  is  a  collar  with  an  exterior 
diameter  of  6.7  inches.  The  part  in  front  of  the  collar  consists  of  four 
threaded  and  four  slotted  sectors  of  about  equal  area.  The  metal 
in  each  of  these  sectors  is  cut  away  sufficiently  to  allow  the  block  to 
swing  clear  of  its  recess.  A  boss  on  the  rear  face  of  the  block  forms 
a  seat  for  the  link  pivot.  A  stud  screwed  into  the  rear  face  of  the  block, 
carrying  an  insulated  copper  plug,  forms  half  of  the  circuit  breaker 
for  the  electric  firing  mechanism.  The  block  is  bored  axially  to  a 
diameter  of  2.5  inches,  and  a  depth  of  2.4  inches  from  the  rear  face. 
The  bore  is  continued  through  the  block  on  a  diameter  of  4.69  inches, 
and  the  front  end  being  counter-bored  to  a  diameter  of  2.1  inches. 
The  bore  in  the  front  end  is  threaded  and  a  plug  having  an  axial  hole 
for  the  firing  pin  is  screwed  into  .it.  A  spline  screw  prevents  this  plug 
from  turning.  The  larger  diameter  bore  at  the  rear  end  is  also  threaded, 
the  thread  being  rectangular  in  form,  and  having  the  same  pitch  as 
that  on  the  exterior  of  the  breechblock.  A  slot  on  the  left-hand  side 
of  this  bore  allows  for  movement  of  the  breaker  when  the  block  is 
in  its  closed  position.  A  notch  in  the  collar  of  the  block  forms  a  seat 
for  the  latch  when  the  block  is  locked  to  the  carrier. 


ARMAMENT  161 

The  carrier  consists  of  a  steel  plate  having  a  lug  for  the  hinge  pin 
at  right  angles  to  its  face.  This  lug  is  so  shaped  as  to  operate  the 
extractor  when  the  breech  is  opened.  The  plate  is  bored  and  threaded 
the  same  as  the  interior  of  the  block,  and  on  line  with  the  axis  of  the 
gun  when  the  breech  is  closed. 

The  latch  locks  the  block  to  the  carrier  when  its  threads  are  dis- 
engaged from  those  of  the  breech  recess,  and  locks  the  carrier  to  the 
gun  when  the  threads  of  the  block  are  engaged  or  partly  engaged 
with  those  of  the  breech  recess.  When  the  carrier  is  being  closed 
against  the  breech  of  the  gun,  an  inclined  face  on  the  latch  slides  against 
a  similar  face  on  the  recess  in  the  breech  of  the  gun,  withdrawing  the 
latch  from  the  notch  in  the  collar  of  the  breechblock,  and  allowing 
the  block  to  rotate.  At  the  same  time,  a  lug  on  the  latch  is  forced  into 
an  undercut  part  of  the  recess  in  the  breech  of  the  gun,  and  held  there 
by  the  collar  of  the  breechblock,  thus  locking  the  carrier  to  the  gun. 

The  carrier  hub  is  a  bronze  cylinder  with  rectangular  head  at  the 
rear  end.  It  forms  the  connection  between  the  breechblock  and  the 
carrier,  and  contains  the  firing  mechanism  complete. 

The  firing  mechanism  is  of  the  type  known  as  continuous-pull  per- 
cussion, combined  with  electric.  It  consists  of  the  following  parts: 
Firing  pin  with  insulation,  firing-pin  sleeve,  firing-pin  guide  and  firing- 
pin  shoulder,  firing-pin  spring,  pin  and  breaker  pin,  cocking  link  and 
stud,  cocking-stud  block.  For  electric  firing,  when  the  block  is  closed, 
the  firing  pin  projects  about  5/100  inch,  or  enough  to  make  contact 
with  the  primer.  The  firing  pin  is  completely  insulated,  and  is  connected 
with  the  circuit  breaker  by  an  insulated  cable  with  standard  connections. 

Action  of  the  firing  mechanism  is  as  follows :  Supposing  the  gun  to 
be  loaded  and  the  block  closed.  The  firing-pin  guide  is  pressed  forward 
by  the  firing-pin  spring  against  the  front  firing-pin  shoulder.  The 
firing  pin  is  thus  pressed  forward  against  the  primer.  The  connection 
is  now  complete  for  electric  firing.  Unless  held  back  by  the  primer, 
the  projection  of  the  firing  pin  in  this  position  is  about  5/100  inch. 
For  percussion  firing  the  breaker  is  pulled  to  the  rear  until  the  cocking 
piece  is  left  from  the  firing-pin  sleeve.  In  this  movement,  the  firing 
pin  is  pulled  to  the  rear  about  8/10  inch.  When  released,  the  spring 
drives  it  forward  until  the  firing-pin  guide  strikes  the  breechblock 
plug.  The  inertia  of  the  firing  pin  and  sleeve  then  carries  them  1/10 
inch  further  forward.  Total  projection  of  the  firing  pin  in  percussion 
firing  is  15/100  inch. 

The  operating  lever  of  the  breech  mechanism  is  hinged  to  the  block- 
carrier  hinge  pin.  It  is  connected  to  the  block  by  a  single  link  with 


162  THE  SERVICE  OF  COAST  ARTILLERY 

the  hinge  pivots  in  the  block  and  lever.  A  latch  fitting  in  a  seat  in  the 
link  pivot  in  the  breechblock  locks  the  lever  when  the  block  is  closed. 

The  extractor  is  hinged  on  a  pin  through  the  lugs  on  the  right- 
hand  side  of  the  gun.  The  rear  end  of  the  tube  is  slotted  to  allow  for 
increased  thickness  of  the  inner  arm  of  the  extractor.  This  inner 
arm  grasps  the  rim  of  the  cartridge  case.  The  outer  arm  has  a  cammed 
surface  against  which  another  cammed  surface  on  the  carrier  plate  slides 
when  the  latter  is  opened.  These  two  cammed  surfaces  are  so  shaped 
as  to  give  the  extractor  an  accelerated  movement  which  ejects  the 
cartridge  case  clear  of  the  gun. 

To  Open  the  Breech. — Rotate  the  handle  to  the  right  until  the 
carrier  plate  comes  to  rest  against  the  extractor.  By  this  movement 
the  lever-latch  plunger  is  withdrawn  from  its  seat,  thereby  allowing  a 
further  pull  on  the  lever  to  rotate  the  block  contra-clockwise  by  means 
of  the  link  through  an  angle  of  45  degrees.  The  threads  of  the  block 
are  now  disengaged  from  those  of  the  breech  recess.  The  block  latch 
is  situated  in  its  notch  in  the  collar  of  the  breechblock,  thereby  locking 
the  carrier  plate  to  the  breechblock  and  enabling  one  by  further  pulling 
on  the  lever  handle  to  swing  the  block  clear  of  the  breech  recess. 
During  the  rotation  of  the  block  the  cam  on  the  breechblock  plug 
retracts  the  firing  pin  by  means  of  the  lock  on  the  firing-pin  sleeve. 
When  the  rear  of  the  carrier  plate  strikes  the  extractor,  its  inner  arm 
is  caused  to  move  to  the  rear,  thus  extracting  the  cartridge  case. 

To  Close  the  Breech. — Rotate  the  handle  to  the  left  until  the 
lever  latch  seats  itself  and  further  motion  is  impossible.  During  this 
operation  the  latch  recess  in  {he  breech  of  the  gun  draws  the  latch 
out  of  its  notch  in  the  block,  thereby  allowing  the  block  to  be 
rotated  in  a  clockwise  direction.  The  latch  then  locks  the  carrier 
to  the  gun,  and  is  prevented  from  unseating  itself  by  the  collar  of 
the  block. 

To  Assemble  the  Breech  Mechanism, — First  assemble  the  latch  and 
spring  to  the  carrier  plate,  then  the  extractor  and  carrier  plate  to  the 
gun.  In  putting  in  the  carrier-plate  hinge  pin,  the  carrier  should 
be  made  to  turn  the  carrier  plate  so  that  an  arrow  marked  on  it  comes 
opposite  a  corresponding  arrow  marked  on  the  gun.  .  Assemble  the 
insulation  on  the  firing  pin,  then  put  the  front  shoulder  over  the 
insulation  and  the  firing-pin  guide  over  the  front  shoulder,  the  rear 
shoulder  and  firing -pin  spring  on  the  firing-pin  sleeve,  and  then  slip 
the  sleeve  over  the  firing-pin  insulation.  The  insulation  washer,  nut 
and  taper  pin  on  the  rear  are  placed  to  the  rear  end  of  the  firing  pin. 
The  breaker,  with  spring  pin  and  cocking  link  are  assembled  to  the 


ARMAMENT  163 

carrier  hub.  Screw  the  carrier  hub  into  the  carrier  plate  until  its 
front  end  is  flush  with  the  front  face  of  the  plate.  Push  the  assembled 
firing  pin  to  its  place  in  the  front  end  of  the  carrier  hub,  at  the  same 
time  pulling  back  on  the  breaker.  Hold  the  breechblock  in  the  closed 
position  against  the  front  face  of  the  carrier  plate.  In  this  position 
screw  the  carrier  hub  to  its  seat  and  tighten  the  locking  screw.  The 
operating  lever  and  link  are  assembled  and  the  block  rotated  until  the 
latch  locks  it  to  the  carrier  plate. 

To  Dismount  the  Breech  Mechanism. — The  operations  for  dis- 
moimting  the  breech  mechanism  are  the  reverse  to  those  given  above 
for  assembling  it. 

Total  length  154.35  inches;  weight  1,950  pounds;  length  of  bore 
50  calibers.  Fixed  ammunition  is  used;  also  projectiles  as  described 
for  the  Driggs-Seabury  gun. 

3-lNCH    (15-POUNDER)     RAPID-FlRE    GlJN,    MODEL    OF    1903 

This  rifle  is  of  Ordnance  Department  manufacture  and  corresponds 
to  the  Bethlehem  Model  of  1902,  except  in  power. 

Total  length  170  inches;  weight  2,692  pounds;  length  of  bore 
55  calibers;  weight  of  projectile  15  pounds;  weight  of  propelling 
charge,  nitro-cellulose  powder,  6.06  pounds. 

Muzzle  velocity  3,000  foot-seconds.  Muzzle  energy  935.8  foot- 
tons.  Maximum  pressure  41,000  pounds  per  square  inch.  Penetration 
in  Krupp  cemented  armor,  at  5,000  yards,  with  uncapped  projectile, 
.85  of  an  inch. 

2.24-lNCH  (6-PouNDER)   R.  F.  GUN,  DRIGGS-SEABURY  MODEL  OF  1898 

This  rifle  follows  the  general  method  of  built-up  forged-steel  con- 
struction. It  consists  of  a  tube,  jacket,  hoop  and  breech  mechanism. 
The  tube  in  enveloped  by  the  jacket  and  hoop  for  a  distance  of  about 
52  inches  from  the  breech  end,  the  two  being  locked  together  by  a 
bronze  sleeve  screwed  on  and  locked  in  place. 

The  sleeve  is  machined  so  as  to  form  upon  each  side  of  its  exterior 
two  parallel  bearing  surfaces  by  which  the  gun  is  supported  in  the 
mount. 

MECHANISM  OF  THE  GUN 

The  jacket  extends  beyond  the  rear  end  of  the  tube  far  enough 
to  form  a  breech  recess  and  is  cut  away  at  the  bottom  to  receive  the 
block. 


164  THE  SERVICE  OF  COAST  ARTILLERY 

The  bore  is  composed  of  a  cartridge  seat,  forcing  slope  and  main 
bore.  There  are  24  grooves  in  the  first  six  guns  manufactured  and 
18  grooves  in  the  others.  The  twist  of  rifling  is  from  0  to  1  turn  in  25.8 
calibers  at  the  muzzle. 

The  breech  recess  is  cut  away  at  the  top  to  form  two  steps  against 
which  corresponding  projections  on  the  block  abut,  and  on  each  side 
to  receive  the  operating  lugs  and  the  pivots  of  the  extractor.  The 
end  of  the  tube  is  cut  away  also  to  receive  the  arms  of  the  extractor. 
A  hole  is  drilled  through  each  cheek  for  the  operating  shaft. 

The  breech  mechanism  (known  as  the  drop-block  system)  consists 
of  the  block,  operating  shaft,  cam  sleeve,  locking  spring,  extractor, 
percussion-firing  lock,  operating  handle  and  associate  parts. 

On  the  top  of  the  breechblock  are  formed  two  locking  shoulders 
arranged  in  steps,  and  on  its  sides  two  operating  lugs  and  rotating 
stops,  on  the  lower  side  of  which  the  extractor-cam  surface  is  formed. 

The  block  is  drilled  through  transversely  for  the  insertion  of  the 
operating-cam  sleeve  and  an  axial  seat  is  formed  in  the  rear  for  the 
firing  "lock.  The  locking  shoulders  engage  against  the  steps  at  the 
top  of  the  breech  recess;  the  under  surfaces  of  the  operating  lugs 
are  in  contact  with  the  cams  of  the  sleeve  while  the  upper  surfaces 
bear  against  the  top  of  the  slots  in  the  sides  of  the  breech  recess. 

The  rotating  stops  limit  the  rotation  of  the  operating  shaft  to  the 
rear  and  are  partly  cut  away  to  clear  the  jacket  when  the  breech  is 
open.  The  extractor-cam  surface  is  so  shaped  as  to  give  a  throw  to 
the  extractor  at  the  end  of  its  movement. 

The  seat  for  the  firing  lock  is  cylindrical  except  at  the  forward  end, 
where  it  is  shaped  for  the  passage  of  the  point  of  the  firing  pin;  the 
rear  end  is  counter  bored  to  a  larger  diameter  and  threaded  to  receive 
the  firing  lock. 

A  seat  for  the  pin  of  the  bracket-locking  spring  is  cut  in  the  rear 
face  of  the  block. 

The  operating  shaft  is  mainly  cylindrical  with  a  journal  at  the  right 
end  and  another  near  the  left.  Adjoining  these  journals  on  the  inside 
the  shaft  is  made  hexagonal  to  fit  corresponding  seats  in  the  sleeve. 
There  is  a  slot  for  the  locking  spring,  also  for  the  key  on  the  inside  of 
the  handle;  the  slot  is  wider  than  the  key.  This  permits  a  small  amount 
of  rotation  of  the  handle  around  the  shaft. 

The  cam  sleeve  consists  of  two  cams  joined  by  a  hollow  cylinder. 
The  interior  of  each  end  is  made  hexagonal  to  fit  the  operating  shaft, 
and  the  cams  are  shaped  to  act  with  the  operating  lugs  of  the  block. 

The  operating  handle  is  a  hollow  rod  with  a  lug  at  one  end  bored 


ARMAMENT  165 

out  to  receive  the  left  end  of  the  operating  shaft.  A  key  let  into  the 
lug  works  in  the  corresponding  slot  in  the  operating  shaft  and  a  short 
slot  is  cut  on  the  right  or  inner  face  of  the  lug  for  the  seat  of  a  lug  on 
the  locking  spring. 

The  locking  spring  is  a  steel  bar  with  two  lugs  on  one  side  and  a 
third  at  the  o-uter  end.  This  last  secures  the  operating  handle;  the 
next  one,  in  conjunction  with  the  handle,  operates  the  spring  and 
locks  the  shaft  to  the  jacket,  while  the  third  serves  to  lock  the  shaft 
in  the  gun. 

The  extractor  is  roughly  Y-shaped.  Two  flanges  on  the  arms 
engage  the  rim  of  the  cartridge  case,  the  stem  forms  the  toe  by  which 
the  extractor  is  operated,  and  two  pivot  lugs  serve  to  support  the 
extractor  in  the  jacket. 

The  percussion-firing  lock  is  called  a  continuous-pull  firing  mechan- 
ism; that  is,  one  in  which  the  pull  on  the  lanyard  first  compresses  the 
firing  spring  and  then  releases  it,  allowing  the  spring  to  drive  forward 
the  pin.  It  consists  of  the  firing  pin,  the  pawl,  the  firing  spring,  the 
bracket  bearing,  the  trigger,  the  trigger  spring,  and  the  bracket- 
locking  spring. 

The  firing  pin  is  mainly  cylindrical,  with  the  taper  point  and  a 
shoulder  in  front  and  a  flattened  section  in  rear.  A  slot  for  assembling 
the  firing  pin  to  the  bracket  bearing  is  cut  just  forward  of  the  flattened 
portion,  a  small  hole  is  drilled  in  rear  of  the  head  of  the  firing  pin  to 
hold  the  end  of  the  firing-pin  spring,  six  longitudinal  grooves  are  cut 
in  the  head  for  gas  vents  and  two  holes  are  drilled  through  the  flattened 
section,  one  for  the  pivot  to  which  the  pawl  is  assembled  and  the  other 
for  the  lanyard. 

The  pawl  is  slotted  to  fit  the  rear  of  the  firing  pin  and  has  a  pivot 
hole  and  a  seat  for  a  small  pin.  The  firing  spring  is  a  coiled  steel-wire 
spring  that  abuts  against  the  head  of  the  firing  pin  in  front  and  the 
bracket  bearing  in  rear.  The  front  end  is  seated  in  a  small  hole  in 
the  pin  and  the  rear  is  held  between  the  bracket  and  a  shoulder  in  a 
counterbore  in  the  block.  The  bracket-bearing  screws  into  the  block, 
closing  the  firing-pin  cavity,  and  serving  as  a  support  for  the  rear  of 
the  firing  pin.  It  also  carries  an  arm  upon  which  the  firing  trigger  is 
pivoted.  It  is  provided  with  a  pin,  which,  working  on  a  longitudinal 
slot  in  the  firing  pin,  prevents  the  latter  from  turning.  On  its  rear 
face  is  riveted  the  bracket-locking  spring,  a  leaf  spring  formed  in  a 
half  circle  and  carrying  at  its  end  a  pin  which  is  pressed  into  a  seat  in 
the  block  when  the  bracket  is  screwed  home. 

The  trigger  is  an  arm  pivoted  on  the  bracket  bearing  and  carrying 


166  THE  SERVICE  OF  COAST  ARTILLERY 

the  cocking  toe.  Near  the  upper  end  a  hole  for  attaching  the  lanyard 
is  drilled,  and  below  this  it  is  slotted  for  the  stop  pin  on  the  pawl. 
The  trigger  spring  is  of  coiled  steel  wire  assembled  around  the  trigger 
pivot,  having  one  end  in  the  bracket  arm  and  the  other  in  the  trigger. 
Its  function  is  to  force  the  trigger  to  the  front  or  normal  position  after 
firing. 

Action  of  the  Breech  Mechanism. — Immediately  after  firing,  the 
block  is  in  its  seat  in  the  breech  recess,  the  operating  handle  is  to  the 
front,  the  lugs  on  the  locking  spring  are  in  their  seats  in  the  handle 
and  the  jacket,  the  operating  lugs  on  the  block  are  supported  in  the 
vertical  portions  of  their  slots  by  the  cams  on  the  cam  sleeve,  the 
flanges  of  the  extractor  engage  the  rim  of  the  case,  the  pivot  lugs  of 
the  extractor  are  in  the  rear  part  of  their  slots,  the  point  of  the  firing 
pin  is  flush  with  the  front  face  of  the  block,  and  the  cocking  toe  is 
forward  of  the  pawl. 

To  Open  the  Breech. — Rotate  the  handle  to  the  rear.  During  the 
first  part  of  this  movement  the  handle  rotates  about  the  shaft,  com- 
pressing the  locking  spring  and  releasing  the  lug  from  its  seat  in  the 
jacket;  then  the  operating  shaft  and  cam  sleeve  rotate  together  to 
the  rear,  and  the  cams  are  moved  so  as  to  permit  the  operating  lugs, 
and  consequently  the  block,  to  descend  until  the  latter  is  disengaged 
from  the  shoulder  at  the  top  of  the  breech  recess;  (if  the  block  does 
not  descend  by  its  own  weight,  the  operating  cams  bearing  on  tops  of 
the  rotating  stops  force  it  down.)  In  this  position  the  cams  abut 
against  the  rotating  stops  and  cause  the  block  to  rotate  with 
the  operating  shaft  until  stopped  by  the  flanges  at  the  bottom 
of  the  breech  recess  between  the  checks  of  the  jacket.  During  the 
rotation  of  the  block  the  extractor  cam  surface  strikes  the  stem  of 
the  extractor  and  forces  the  pivot  lugs  forward  in  their  slots,  causing 
the  arms  of  the  extractor  to  move  to  the  rear  sufficiently  to  loosen 
the  case  in  its  seat;  when  the  pivot  lugs  bring  up  against  the  shoulder 
of  the  slots,  the  cam  surface  continuing  to  act  rotates  the  extractor 
about  the  lugs,  giving  a  quick  throw  that  fully  ejects  the  case. 

To  Close  the  Breech. — Rotate  the  handle  smartly  to  the  front  until 
it  comes  to  a  stop.  The  action  of  the  mechanism  is  the  reverse  of 
opening. 

To  Fire  the  Gun. — Insert  the  hook  of  the  lanyard  in  the  eye  of 
the  trigger  and  pull  until  the  firing  pin  is  released.  The  cocking  toe, 
except  when  forced  oo  the  rear,  is  constrained  by  the  trigger  spring 
to  remain  against  the  face  of  the  bracket  bearing,  forward  of  the  pawl, 
so  that  when  the  trigger  is  pulled,  carrying  the  toe  to  the  rear,  the 


ARMAMENT  167 

pawl  and  consequently  the  firing  pin  go  with  it.  As  the  toe  rotates 
while  the  pawl  is  forced  to  move  in  a  straight  line,  the  latter  is  released 
when  it  has  been  retracted  about  f  inch,  and  moving  forward  under 
the  action  of  the  spring,  the  pin  impinges  against  the  primer.  When 
the  tension  on  the  lanyard  is  released  the  trigger  moves  forward,  under 
the  action  of  its  spring,  until  the  toe  strikes  the  bracket  bearing.  In 
this  movement  the  pawl  is  first  rotated  by  the  toe,  clearing  the  latter, 
and  afterwards  rotated  back  by  its  pin,  passing  into  the  slot  in  the 
trigger  arm.  The  firing  toe  and  pawl  are  thus  again  ready  for  firing. 
The  point  of  the  firing  pin  is  kept  normally  flush  with  the  front  face 
of  the  block,  because  the  firing-pin  spring,  being  fastened  at  both  ends 
and  properly  adjusted,  works  in  both  directions  and  holds  the  pin  in 
that  position.  In  firing,  the  momentum  given  the  pin  by  the  spring 
carries  it  beyond  its  point  of  rest  with  sufficient  force  to  explode  the 
primer. 

In  case  the  firing  toe  does  not  engage  the  pawl,  rotate  the  pawl  to 
the  front  with  the  hand.  The  gun  may  be  fired,  in  case  the  trigger 
becomes  injured,  by  attaching  the  lanyard  directly  to  the  eye  of  the 
firing  pin.  In  case  of  a  misfire  additional  blows  may  be  given  the 
primer  by  slacking  on  the  lanyard  to  allow  the  toe  to  again  engage 
the  pawl. 

To  Assemble  the  Breech  Mechanism. — The  shoulder  bar  being  out, 
put  the  block  in  place  from  below,  and  hold  it  firmly  against  the  top 
of  the  breech  recess;  insert  the  extractor,  arms  upward,  flanges  next 
to  the  tube,  and  engage  the  pivot  lugs  in  their  slots;  lower  the  block, 
let  go  the  extractor,  and  incline  the  block  so  that  the  cam-sleeve  seat 
is  clear.  Place  the  cam  sleeve  in  position,  larger  end  to  the  left,  so 
that  the  cams  lie  between  the  operating  lugs  and  the  rotating  stops; 
keeping  a  rearward  pressure  on  the  cam  sleeve  as  long  as  possible, 
move  the  block  slowly  into  the  open  position;  by  a  pressure  underneath 
the  block,  line  up  the  holes  for  the  operating  shaft;  place  the  locking 
spring  in  its  slot  in  the  operating  shaft  and  seat  the  latter,  keeping  the 
slot  on  top,  and  compressing  the  spring;  put  on  the  operating  handle, 
partly  close  the  block,  and  screw  the  firing  lock  home  until  the  pin 
of  the  locking  spring  enters  its  seat;  close  the  breech;  the  handle 
should  then  point  to  the  front  and  be  nearly  parallel  to  the  axis  of  the 
bore.  The  firing  lock  is  furnished  assembled. 

To  Dismount  the  Breech  Mechanism. — Reverse  the  operation  of 
assembling.  The  locking  spring  must  be  compressed  until  its  locking 
lug  is  free  from  the  circumferential  slot  in  the  left  cheek  of  the  gun; 
the  block  should  be  supported  by  the  hand  while  the  shaft  is  being 


168 


THE  SERVICE  OF  COAST  ARTILLERY 


driven  out.  For  this  operation  use  a  piece  of  wood  or  a  copper 
drift. 

Sights. — Telescopic  sights  have  been  issued  with  some  of  these  guns 
and  mounts.  When  so  issued  th6y  are  placed,  when  in  use,  upon  a 
sight  bracket  which  is  fastened  to  the  right  trunnion  of  the  oscillating 
slide  of  the  mount.  Such  brackets  are  attached  to  all  mounts  of  the 
modification  of  this  model. 

Total  length  118.12  inches;  weight  845  pounds;  length  of  bore  50 
calibers;  weight  of  projectile  6  pounds;  weight  of  charge,  nitre-cellulose 
powder,  1.35  pounds;  nitroglycerine  1.25  pounds. 

Muzzle  velocity  2,400  foot-seconds.  Muzzle  energy  240  foot-tons. 
Maximum  pressure  37,460  pounds  per  square  inch.  Penetration  in 
Krupp  cemented  armor  .4  inch. 

2.24-lNCH  (6-PouNDEn)  R.  F.  GUN,  DRIGGS-SEABURY  MODEL  OF  1900 

(See  Fig.  16) 


FIG.  16.— 2.24-inch  (6-pounder)  R.  F.,  D.-S.  Gun,  M.  1900.     Interrupted  Thread 
Breech  Mechanism.     Mounted  on  Wheeled  Mount. 

This  rifle  is  essentially  the  same  as  the  model  of  1898,  except 
that  the  breech  recess  in  the  jacket  is  differently  shaped  and  is 
threaded  and  slotted  to  accommodate  the  interrupted-thread  mech- 
anism. 


ARMAMENT  169 


MECHANISM  OF  THE  GUN 

The  breech  mechanism  (known  as  the  interrupted-thread  system) 
consists  of  the  block,  carrier  plate  and  ring,  operating  lever,  hinge  pin, 
lever  pin,  firing  mechanism,  locking  bolt  and  spring,  extractor,  and 
associate  parts. 

The  breechblock  has  two  full  threads  at  the  rear  end  on  which  the 
carrier-plate  ring  is  screwed.  In  front  of  these  there  are  three  threaded 
and  three  interrupted  sectors.  The  interior  of  the  block  is  hollowed  out 
to  receive  the  hub  of  the  carrier  plate  which  carries  the  firing  mechanism. 
The  front  end  of  this  cavity  is  conical,  corresponding  in  shape  to  the 
head  of  the  firing  pin,  and  serves  as  a  stop  to  limit  the  forward  move- 
ment of  the  pin.  A  small  safety  screw,  inserted  from  the  front  face 
of  the  block,  projects  into  this  cavity.  Its  function  is  described  in 
connection  with  the  description  of  the  firing  pin.  A  cylindrical  pro- 
jection on  the  rear  face  of  the  block  forms  a  stop  which,  rotating  in  a 
limited  annular  groove  in  the  front  face  of  the  carrier  plate,  limits 
the  rotation  of  the  block. 

The  carrier  plate  carries  all  the  mechanism  for  operating  the  block 
and  the  firing  mechanism.  It  is  hinged  to  lugs  on  the  gun  and  has 
two  projecting  lugs  on  its  rear  face  to  which  the  operating  lever  is 
hinged.  On  the  front  face  is  a  projecting  hub  which  supports  the 
block  and  within  which  the  firing  pin  and  mechanism  are  placed. 
On  its  front  there  is  also  a  counterbored  seat  in  which  the  carrier-plate 
ring  is  set  and  secured  by  two  screws. 

A  bolt  for  locking  the  block  to  the  carrier  in  the  open  position 
passes  through  the  carrier-plate  ring,  being  forced  forward  by  its  spring. 
When  in  the  forward  position  a  projection  on  the  bolt  enters  a  recess 
in  the  block,  locking  it  to  the  carrier.  When  the  carrier  is  closed  the 
bolt  is  held  in  the  rear,  its  front  end  being  in  contact  with  the  face  of 
the  breech. 

The  operating  lever  projects  through  a  slot  in  the  carrier  plate 
and  has  a  knob  in  front  bearing  in  a  slot  in  the  rear  face  of  the  breech- 
block. The  lever-pin  hole  in  the  operating  lever  is  elongated,  and  a 
locking  lug  is  formed  on  the  front  edge  of  the  lever,  which,  at  the  final 
motion  of  closing,  is  made  to  enter  a  slot  in  the  rear  face  of  the  block, 
thus  preventing  rotation  of  the  block  due  to  the  powder  pressure. 
The  lever-catch  plunger  in  its  spring  are  assembled  in  the  powder- 
lever  lug.  Their  object  is  to  prevent  rotation  of  the  operating  lever 
in  counter  recoil. 


170  THE  SERVICE  OF  COAST  ARTILLERY 

The  extractor  has  trunnions  resting  in  slots  in  the  hinge-pin  lugs. 
It  is  operated  by  a  cam  surface  on  the  carrier  plate. 

The  firing  mechanism  consists  of  the  firing  pin  and  spring,  the  pawl, 
the  trigger,  and  trigger  spring,  and  the  lanyard  button.  The  firing 
pin  is  composed  of  two  parts,  the  body  and  the  head.  The  body  is 
cylindrical,  except  for  a  short  distance  near  the  center,  where  it  is  cut 
away  on  one  side  to  clear  the  cocking  toe  on  the  trigger.  At  this 
point  also  a  lug  is  formed  upon  the  top  of  the  pin  to  which  the  pawl  is 
pivoted.  The  rear  cylindrical  part  has  two  longitudinal  grooves  as 
gas  vents,  and  the  end  of  the  pin  is  provided  with  a  lanyard  eye.  The 
front  end  of  the  body  of  the  pin  is  drilled  and  tapped  to  receive  the  head, 
which  is  screwed  in  and  secured  by  a  small  pin.  The  head  itself  is 
cone-shaped,  the  apex  being  drawn  out  and  hardened  to  form  the  firing 
point.  The  base  of  the  cone  is  grooved  longitudinally  to  permit  the 
escape  of  gas  in  the  event  of  a  blow-back.  A  circular  recess  is  made 
in  the  side  of  the  cone  in  which  the  end  of  the  safety  screw  pin  is  seated 
when  the  block  is  closed  and  locked.  At  other  times  the  rotation  of 
the  block  has  removed  the  screw  from  its  position  opposite  the  recess 
and  it  bears  against  the  side  of  the  firing-pin  head,  thus  preventing 
the  projection  of  the  pin  through  the  block  and  the  resulting  possi- 
bility of  a  premature  discharge. 

The  firing-pin  spring  is  a  coiled  steel  spring  mounted  on  the  body 
of  the  firing  pin  between  its  head  and  the  pawl  lug.  The  front  end  is 
bent  to  fit  into  a  hole  drilled  in  the  body  close  to  the  head,  while  the 
rear  end  is  brought  forward  over  the  coils  parallel  with  the  body,  and 
in  its  normal  position  abuts  against  the  shoulder  at  the  front  of  the 
block.  In  this  position  the  firing  point  is  held  retracted  within  the 
block,  as  a  movement  to  the  front  would  extend  the  spring.  In  the 
firing  the  momentum  of  the  firing  pin  carries  it  forward  beyond  its 
point  of  rest  and  against  the  action  of  the  spring  far  enough  to  explode 
the  primer.  To  remove  the  firing  spring  it  is  necessary  to  take  off 
the  firing-pin  head. 

The  trigger  is  an  arm  having  at  one  end  a  lug  to  form  a  long  pivot 
bearing  and  at  the  other  a  hook  over  which  the  lanyard  button  passes. 
Upon  one  side  of  the  arm  is  formed  the  cocking  toe  which  engages  the 
pawl,  and  on  the  same  side  near  the  upper  end  is  a  short  slot  in  which 
a  projecting  pin  on  the  pawl  is  caught  in  the  forward  movement  of 
the  trigger  after  firing. 

The  trigger  spring  is  coiled  around  the  trigger  pivot  and  secured 
at  both  ends.  Its  action  is  to  force  the  trigger  forward  after  firing 
and  thus  engage  the  pawl  again  in  readiness  for  the  next  shot. 


ARMAMENT  171 

The  lanyard  button  is  a  straight  piece,  slotted  out  to  pass  over 
and  engage  the  hook  on  the  trigger,  and  also  provided  with  a  lanyard 
eye  at  its  rear  end.  It  extends  to  the  rear  through  a  hole  in  the  carrier 
plate,  and  is  prevented  from  being  drawn  to  the  front  through  the 
plate  by  a  button-shaped  enlargement. 

To  Open  the  Breech. — The  first  motion  of  the  operating  lever  to 
open  moves  it  to  the  rear,  due  to  its  elongated  pivot  bearing,  and 
unlocks  the  lug  on  its  front  edge  from  the  slot  in  the  breechblock. 
The  knob  on  the  operating  lever  then  causes  the  block  to  rotate  until 
its  threads  are  unlocked  from  those  of  the  breech  recess.  Further 
rotation  of  the  blgck  around  its  axis  is  prevented  by  its  stop  reaching 
the  end  of  the  groove  in  the  carrier  plate;  rotation,  as  a  whole,  takes 
place  around  the  hinge  pin.  As  soon  as  this  rotation  begins  the  lock- 
bolt  spring  presses  the  bolt  forward,  locking  the  block  to  the  carrier 
plate,  and  the  extractor  is  constrained  to  move  on  its  cam  bearings, 
causing  the  point  to  withdraw  the  cartridge  case  at  first  slowly  and 
then  rapidly. 

The  operation  of  closing  the  block  is  the  reverse  of  the  above. 

The  firing  mechanism,  being  of  the  continuous-pull  type,  is  not 
operated  in  any  way  by  the  operation  of  the  block. 

To  Fire  the  Gun. — Insert  the  hook  of  the  lanyard  in  the  eye  of 
the  lanyard  button  and  pull  until  the  firing  pin  is  released.  Pulling 
the  lanyard  button  causes  the  trigger  to  rotate  around  its  pin.  The 
cocking  toe  of  the  trigger  catches  the  pawl  and  the  firing  pin  is  pulled 
to  the  rear  against  its  spring  until  the  short  arm  slides  off  the  pawl, 
when  the  firing  pin  is  released  and  is  driven  forward  by  its  spring. 
When  the  pull  on  the  lanyard  is  released  the  trigger  spring  rotates 
the  trigger  forward,  causing  the  toe  to  pass  the  pawl.  The  long  arm 
then  strikes  a  pin  on  the  pawl,  causing  the  pawl  to  rotate  downward, 
so  as  to  be  caught  by  the  toe  of  the  trigger,  when  the  firing  mechanism 
is  again  ready  for  firing. 

To  Assemble  the  Breech  Mechanism. — Seat  the  extractor.  Put  in 
the  block-locking  bolt  and  spring  in  the  carrier  plate.  Assemble 
the  carrier  ring  in  the  carrier  plate,  securing  it  by  the  screws,  top  and 
bottom.  Slide  the  firing  pin  with  its  spring  and  pawl  assembled  into 
its  seat  from  the  front  of  the  carrier  plate.  Slip  the  trigger  containing 
its  spring  into  place  from  beneath,  taking  care  that  the  exposed  end  of 
the  spring  enters  its  seat  in  the  carrier  plate;  insert  the  trigger  pin 
carefully  so  as  not  to  displace  the  coils  of  the  spring.  Pass  the  lanyard 
button  from  the  rear  through  the  slot  in  the  carrier  plate  and  hook  it 
over  the  trigger,  lifting  the  pawl  so  that  the  trigger  may  be  pulled 


172  THE  SERVICE  OF  COAST  ARTILLERY 

back  far  enough  for  that  purpose.  Holding  the  trigger  in  that  position 
by  means  of  the  lanyard  button,  slip  the  block  over  the  hub  of  the 
carrier  plate  and  screw  it  home  in  the  carrier  ring.  Seat  the  carrier 
plate  on  the  gun  with  the  block  exposed  and  insert  the  hinge  pin.  Put 
the  lever-catch  plunger  and  spring  in  its  seat,  press  it  down  and  enter 
the  cotter  pin.  Push  in  the  block-locking  plunger,  rotate  the  block 
to  its  closed  position  and  insert  the  operating  lever  in  its  seat.  In 
this  position  the  lever  will  be  home  against  the  carrier  plate.  Insert 
the  operating-lever  pin  and  enter  its  cotter  pin.  Swing  the  block 
and  carrier  to  the  full  open  position  by  means  of  the  lever,  and  by 
further  pulling  the  latter  rotate  the  block  to  its  proper  position  for 
entering  the  breech. 

If  an  attempt  is  made  to  close  the  breech  before  the  last  operation 
the  block  will  jam. 

To  Dismount  the  Breech  Mechanism. — Reverse  the  preceding  ope- 
rations. Care  should  be  taken  not  to  snap  the  firing  pin  except  when 
the  block  is  closed  and  locked,  as  in  any  other  position  the  firing-pin 
head  will  strike  the  end  of  the  safety  screw.  A  few  such  blows  will 
bend  or  break  this  screw. 


2.24-lNCH  (6-PouNDER)   R.-F.    GUN,  AMERICAN   ORDNANCE   Co.   Mm 

This  rifle  follows  the  general  method  of  built-up  forged-steel  con- 
struction. It  consists  of  a  tube,  jacket,  hoop,  and  breech  mechanism. 
The  tube  is  enveloped  for  a  distance  of  42.90  inches  from  the  breech 
end  by  the  jacket  and  hoop.  The  jacket  is  assembled  from  the  rear, 
the  end  of  the  tube  abutting  against  a  shoulder  in  the  former.  The 
hoop  is  assembled  from  the  front,  the  two  parts  being  locked  together 
by  a  bronze  sleeve  with  screws  over  the  joint,  and  is  held  in  place  by  a 
key.  A  shoulder  formed  in  the  tube  abuts  against  a  corresponding 
shoulder  in  the  hoop  and  prevents  forward  movement  of  the  tube. 
The  exterior  of  the  bronze  sleeve  is  machined  to  form  parallel  bearing 
surfaces  or  guides  by  which  the  gun  is  supported  in  the  mount. 

The  portion  of  the  jacket  in  the  rear  of  the  tube  is  enlarged  to  form 
the  recess  for  the  breechblock  and  extractors. 

The  bore,  which  is  50  calibers  in  length,  is  composed  of  a  seat  for 
the  cartridge,  a  forcing  slope,  and  a  main  bore,  which  is  2.244  inches 
in  diameter  between  lands. 

The  rifling  begins  at  a  point  12.873  inches  from  the  breech  end  of 
the  tube  with  a  right-hand  twist,  increasing  from  0  to  1  turn  in  26.36 
calibers  at  the  muzzle. 


ARMAMENT  173 

The  top  of  the  breech  recess  is  rounded  and  has  four  circumferential 
grooves  into  which  corresponding  ribs  on  the  block  fit  when  the  latter 
is  locked.  Seats  for  the  pivots  of  the  extractors  are  drilled  on  either 
side  near  the  front  of  the  breech  recess,  and  a  transverse  hole  or  bearing, 
for  the  main  bolt  is  drilled  through  each  cheek.  A  guide  bolt  is  also 
screwed  into  each  cheek,  the  end  projecting  slightly  into  the  breech 
recess. 

Breech  Mechanism. — These  guns  are  fitted  with  the  Driggs-Schroeder 
breech  mechanism,  the  principal  parts  of  which  are  the  block,  face  plate, 
main  bolt,  cam,  operating  handle,  lever  lock,  lever-detent  spring, 
extractors  and  firing  mechanism. 

The  general  shape  of  the  block  is  the  same  as  that  of  the  breech 
recess.  On  its  rounded  top  are  formed  four  ribs  which  serve  to  lock 
the  'block  in  the  firing  position  and  transmit  the  thrust  to  the  jacket. 
On  each  side  of  the  block  is  a  curved  slot  in  which  work  the  ends  of 
the  guide  bolts.  Undercut  slots  are  cut  in  the  front  and  rear  faces 
of  the  block  to  receive  the  face  plate  and  the  sear,  and  its  interior  is 
hollowed  out  for  the  cam  and  the  firing  pin.  Recesses  are  also  cut  in 
each  side  of  the  front  face  for  the  extractors  and  surfaces  for  operating 
the  same,  formed  on  the  sides  of  the  block. 

Access  to  the  interior  of  the  block  is  gained  through  an  opening 
in  the  front  face,  which,  when  the  block  is  assembled,  is  closed  by 
the  face  plate.  The  latter  is  a  steel  plate  seated  in  an  undercut  slot 
and  secured  in  place  by  the  front  end  of  the  sear  spring.  It  is  drilled 
to  permit  the  passage  of  the  point  of  the  firing  pin,  and  has  a  thumb 
notch  for  easy  assembling. 

The  main  bolt  consists  of  two  cylindrical  surfaces  of  different 
diameters  joined  by  a  hexagonal  seat  for  the  cam.  It  passes  through 
an  elongated  hole  in  the  block  and  the  cylindrical  ends  fit  into  the 
supporting  bearings  drilled  through  the  cheeks  of  the  breech  recess. 
On  the  smaller  end  which  projects  through  the  left  cheek  the  operating 
handle  is  fitted  and  secured  to  it  by  a  feather  lug  and  the  lever  lock. 
The  lever  lock  is  a  circular-shaped  lever  pivoted  to  the  operating 
handle  just  above  the  lug  and  carrying  on  its  under  side  a  projection 
which  passes  through  a  seat  in  the  lug  and  engages  in  a  seat  in  the 
main  bolt,  thus  securing  the  handle  in  place. 

The  handle  is  prevented  from  movement  in  counter  recoil  by  the 
lever-detent  spring,  a  spring  circular  in  shape  and  dovetailed  to  the 
handle  lug.  The  free  end  partly  embraces  the  lever-stop  pin  when 
the  breech  is  closed,  thus  preventing  movement  of  the  handle. 

The  cam  is  a  short  sleeve  mounted  upon  the  main  bolt  within  the 


174  THE  SERVICE  OF  COAST  ARTILLERY 

block.  It  has  a  projecting  cam  surface  which  bears  against  the  interior 
of  the  block  and  controls  the  movement  of  the  latter,  and  in  addition 
a  shoulder,  which  by  engaging  an  arm  on  the  firing  pin,  cocks  the  pin 
during  the  opening  movement. 

There  are  two  extractors,  one  on  each  side.  Each  consists  of  an 
arm,  slightly  bent,  on  which  is  formed  at  right  angles  a  pivot  that 
seats  in  a  bearing  drilled  in  the  side  of  the  breech  recess. 

The  upper  end  of  the  arm  carries  the  flange  which  engages  the 
cartridge  case,  while  on  the  ower  end  is  formed  a  cam  which  works 
against  a  corresponding  surface  on  the  block. 

The  Firing  Mechanism  is  composed  of  the  firing  pin,  the  firing-pin 
spring,  the  sear,  and  the  sear  spring. 

The  firing  pin  consists  of  a  cylindrical  body  carrying  on  the  under- 
side the  full-cock  stud  and  the  cocking  arm  and  terminating  in  an  eye 
for  the  drill-washer  support  in  rear.  On  the  upper  side  of  the  front 
end  of  the  body  is  formed  a  lug,  which  is  drilled  and  slotted  to  receive 
the  split  stem  of  the  point.  The  firing-pin  point  is  made  in  the  form  of 
a  short  spring  split  pin,  the  split  end  of  which  carries  two  locking 
shoulders.  The  lug  on  the  firing-pin  body  is  slotted  to  permit  the 
passage  of  these  shoulders,  so  that  when  the  head  is  pressed  home 
and  partly  rotated  a  bayonet  joint  is  formed.  The  spring  effect  tends 
to  spread  the  locking  shoulders  and  prevent  accidental  rotation  of 
the  head.  The  firing  spring  lies  between  the  lug  of  the  firing  pin  in 
front  and  a  shoulder  of  the  block  in  rear. 

The  sear  is  a  simple  slide  working  in  an  undercut  slot  in  the  rear 
face  of  the  block.  Actuated  by  the  sear  spring,  it  presses  up  against 
the  firing  pin  and  engages  the  full-cock  stud  when  the  pin  is  retracted. 
Near  its  lower  end  a  projecting  lanyard  eye  is  formed. 

The  sear  spring  is  a  flat  spring  enlarged  at  both  ends,  the  rear  end 
being  notched  to  engage  the  sear,  while  the  front  end  is  cylindrical 
and  serves  both  as  a  fulcrum  for  the  spring  and  as  a  retaining  pin  for 
the  face  plate. 

In  the  open  position  the  block  is  supported  by  the  tray,  a  channel- 
shaped  forging,  which  is  secured  to  the  rear  ends  of  the  cheeks  by 
screws. 

To  Open  the  Breech. — Turn  the  operating  handle  smartly  to  the 
rear.  This  movement  unlocks  the  main  bolt  by  releasing  the  lever- 
detent  spring  from  the  stop  pin,  and  rotates  the  main  bolt  and  cam. 
The  first  movement  of  the  latter  starts  the  retraction  of  the  firing  pin. 
As  soon  as  the  latter  is  retracted  within  the  block  the  cam  begins  to 
act  on  the  block,  forcing  it  down  until  the  ribs  on  the  block  clear  the 


ARMAMENT  175 

grooves  in  the  gun.  The  cam  and  guide  bolts  then  cause  the  blocks 
to  rotate  backward  around  the  main  bolt  until  its  front  face  is  parallel 
to  the  axis  of  the  gun.  During  this  movement  the  firing  pin  has  been 
fully  retracted  and  caught  by  the  sear.  As  the  block  rotates  backward 
the  lower  arms  of  the  extractor  follows  the  cam  surfaces  on  the  former, 
causing  the  extractors  to  start  the  empty  case  slowly  at  first  and  after- 
ward to  eject  it  quickly. 

The  breech  is  closed  by  fuming  the  operating  handle  to  the  front. 
The  block  is  first  turned,  then  raised  and  locked,  the  firing  pin  being 
left  in  the  full-cock  position. 

To  Fire  the  Gun. — Pass  the  lanyard  beneath  the  tray  and  hook 
it  into  the  eye  on  the  sear.  A  quick  pull  on  the  lanyard  will  draw 
drown  the  sear  and  release  the  firing  pin.  To  permit  of  snapping  the 
firing  pin  for  drill  purposes  and  without  a  cartridge  case  in  the  gun,  a 
rubber  ring,  called  the  drill  washer,  is  slipped  over  the  rear  end  of  the 
firing  pin  and  held  in  place  by  the  washer  support,  which  passes  through 
the  eye  on  the  end  of  the  pin.  When  the  trigger  is  snapped  under 
drill  conditions  this  rubber  ring  acts  as  a  buffer  between  the  rear  face 
of  the  block  and  the  support  and  thus  lessens  the  shock  on  the  firing 
pin. 

The  drill  washer  does  not  interfere  with  firing  the  gun,  and  should 
be  left  on  at  all  times  in  order  to  avoid  the  possibility  of  snapping  the 
trigger  without  it. 

To  Dismount  the  Breech  Mechanism. — Cock  the  firing  pin  either 
by  opening  and  closing  the  breech  or  by  pulling  it  to  the  rear  with 
the  breech-mechanism  tool  until  the  sear  engages.  Remove  the  handle, 
having  first  raised  its  locking  lever. 

Withdraw  the  main  bolt,  supporting  the  block  from  beneath  by  the 
hand;  remove  the  block  by  lowering  it  until  the  ribs  on  top  are  dis- 
engaged, and  then  withdrawing  it  straight  to  the  rear  until  clear  of 
the  gun. 

Lay  the  block  on  its  right  side  on  a  wooden  surface,  withdraw  the 
sear  spring  from  the  front  and  slip  out  the  face  plate;  turn  the  block 
face  down  and  pull  down  the  sear,  thus  liberating  the  firing  pin  and 
spring;  lift  up  the  block,  and  the  cam,  firing  pin,  and  spring  will  drop 
out  clear. 

Care  should  be  taken  to  see  that  the  firing  pin  is  cocked  before 
attempting  to  remove  the  face  plate;  otherwise  the  point  of  the  pin 
will  be  bent  or  broken  by  the  plate.  If  there  is  no  wood  surface  con- 
venient for  snapping  the  firing  pin  into,  hold  it  back  with  the  tool  and 
ease  it  forward  on  removing  the  sear. 


176  THE  SERVICE  OF  COAST  ARTILLERY 

To  Assemble  the  Breech  Mechanism. — Reverse  the  preceding 
operations.  Put  in  successively  the  firing  spring,  firing  pin,  and  cam; 
the  front  side  of  the  latter  is  marked  "Out."  Put  on  the  face  plate, 
being  careful  to  see  that  the  firing  pin  is  retracted  while  so  doing. 
Insert  the  sear  spring  and  engage  the  notch  at  its  rear  end  with  the  sear. 
Replace  the  block  in  the  breech  in  the  closed  position  and  insert  the 
main  bolt,  bringing  the  arrow  on  its  head  in  line  with  the  arrow  on  the 
cheek  in  order  to  insure  the  proper  location  of  the  cam  on  its  hexagonal 
seat.  Put  on  the  handle  and  close  the  locking  lever  into  its  seat,  taking 
care  that  it  is  pushed  home. 


FIRING   MECHANISM,    MODEL   OF    1903 

USED  ON  ALL  8-lNCH,   10-lNCH  AND    12-INCH    RlFLES,  AND   12-INCH 

MORTARS 

(Plates  V  and  IX) 

The  principal  parts  of  the  firing  mechanism,  of  the  above  model, 
are  hinged  collar,  housing,  slide,  and  firing  leaf. 

The  hinged  collar  embraces  the  rear  end  of  the  spindle,  two'  ribs 
on  its  inner  surface  engaging  in  corresponding  grooves  in  the  spindle. 

The  housing  screws  over  the  hinged  collar,  which  is  threaded  to 
receive  it,  and  a  spring  catch  locks  the  collar  to  the  housing  when  it  is 
fully  screwed  home.  The  collar  is  thus  prevented  from  opening  and 
secures  the  housing  to  the  spindle. 

A  guide  bar  projects  from  the  right  side  of  the  housing  into  a  longi- 
tudinal groove  cut  in  the  block  recess  and  causes  the  housing  to  rotate 
with  the  block. 

The  slide  travels  vertically  in  grooves  cut  in  the  rear  face  of  the 
housing  and  when  in  its  lowest  position  holds  the  primer  to  place  in 
the  primer  seat.  Its  motion  is  limited  by  the  slide  stop  on  the  left  side 
of  the  housing.  The  slide  catch  serves  to  lock  it  in  place  when  lowered, 
and  to  support  it  at  the  proper  height  to  allow  the  primer  to  be  inserted 
when  raised. 

The  ejector  is  an  L-shaped  piece  with  trunnions  at  its  angle,  about 
which  it  swings,  and  which  enter  two  slots  cut  for  them  in  the  housing. 
The  lower  arm  of  this  extractor  is  fork-shaped  and  hangs  over  the  mouth 
of  the  primer  seat  under  the  head  of  the  primer.  The  horizontal  arm 
projects  to  the  rear  into  a  recess  in  the  slide,  and  when  the  latter  is 
lifted  this  arm  is  carried  upward  and  the  ejector  rotated  about  its 


ARMAMENT  177 

trunnions  so  as  to  throw  the  horizontal  arm  to  the  rear,  ejecting  the 
primer. 

The  firing  leaf  is  pivoted  to  the  slide  at  its  upper  end.  It  has  a 
vertical  slot  cut  in  its  lower  edge  through  which  the  wire  of  the  primer 
projects  when  the  slide  is  in  its  lower  or  locked  position.  At  the 
right-hand  lower  corner  of  the  leaf  is  an  eye  into  which  the  lanyard 
is  hooked  for  friction  firing.  When  the  leaf  is  drawn  to  the  rear  it 
engages  the  button  on  the  end  of  the  primer  wire  and  draws  the  wire 
out  and  fires  the  primer. 

Electric  connection  with  the  primer  is  made  through  the  two  brass 
arms  of  the  contact  clip  which  embrace  the  head  of  the  primer.  The 
contact  clip  is  held  in  place  by  a  housing  which  is  secured  to  the  rear 
face  of  the  leaf.  The  electric-cable  terminal  is  made  of  a  piece  of  steel 
rod  bent  at  a  right  angle.  To  one  arm  is  attached  the  electric  cable; 
the  other  arm  is  slit  to  form  a  spring  which  is  inserted  into  a  hole  in 
the  contact-clip  housing  on  the  firing  leaf. 

A  safety  bar  prevents  accidental  firing  of  the  piece  by  the  lanyard 
before  the  breech  is  locked;  and  a  circuit  breaker  serves  to  prevent 
firing  the  piece  by  electricity  before  the  breech  is  locked. 

The  first  motion  of  rotation  of  the  block  to  unlock  the  breech 
forces  the  safety  bar  inward  so  as  to  engage  the  leaf  and  prevent  its 
being  drawn  to  the  rear,  while  at  the  same  time  the  electric  circuit  is 
broken  by  the  same  movement  of  rotation. 

A  safety  lug  on  the  right  side  of  the  housing  engages  a  groove  in 
the  firing  leaf  and  prevents  the  latter  from  being  drawn  to  the  rear 
before  the  breechblock  is  rotated  to  its  locked  position.  The  last  part 
of  the  motion  of  lowering  the  slide  makes  electric  connection  with  the 
primer.  It  will  be  seen  from  this  that  accidental  firing  of  the  piece  is 
impossible  until  the  breech  is  locked  and  the  slide  of  the  firing  mechan- 
ism is  in  its  lower  or  locked  position. 

The  circuit  breaker  is  of  bronze  and  consists  of  two  principal 
pieces  which  are  brought  together  when  the  block  is  rotated  to  its 
locked  position.  A  plunger  working  under  the  pressure  of  a  spring- 
serves  to  make  electric  contact  between  the  two  pieces.  Both  parts 
of  the  circuit  breaker  are  insulated  from  the  piece  by  vulcanized 
fiber.  The  electric  cable  is  attached  to  the  circuit  breaker  by  a  spring- 
fork. 

Instructions  for  the  Care  and  Use  of  Seacoast  Firing  Mechanism, 
Model  of  1903. — While  this  mechanism  forms  part  of  a  heavy  gun,  it 
is  in  itself  small  and  light;  the  several  parts  are  very  closely  adjusted, 
and  it  has  been  necessary  to  make  the  clearances  very  small.  The 


178  THE  SERVICE  OF  COAST  ARTILLERY 

greatest  care  must  be  exercised,  therefore,  in  keeping  the  mechanism 
well  oiled  and  free  from  rust  and  dirt. 

It  should  not  be  left  on  the  gun  when  not  in  use,  but  should  be 
kept  habitually  in  the  small  box  provided  for  it,  and  stored  in  the 
armament  chest. 

To  Assemble  the  Mechanism  on  the  Gun. — Clasp  the  hinged  collar 
over  the  end  of  the  spindle  with  the  two  ribs  of  the  collar  engaging 
in  the  corresponding  grooves  of  the  spindle,  keeping  the  hinge  at  the 
top. 

Take  the  mechanism  in  the  right  hand,  holding  the  collar  with  the 
left,  and  put  the  mechanism  over  the  end  of  the  collar,  screwing  the 
latter  to  the  left  until  the  catch  on  the  under  side  of  the  mechanism 
engages  and  locks  it  into  position.  While  doing  this,  see  that  the  guide 
bar  which  projects  from  the  right  side  of  the  mechanism  enters  the 
groove  cut  in  the  breechblock  for  it,  and  that  the  pin  on  the  safety- 
bar  slide  (which  is  attached  to  the  gun),  enters  the  hole  in  the  outer 
end  of  the  safety  bar  of  the  mechanism. 

Do  not  attempt  to  use  the  mechanism  until  it  is  absolutely  certain  that 
the  collar  has  been  screwed  entirely  home  and  locked. 

After  the  primer  has  been  inserted  lower  the  slide  until  the  catch 
engages  in  the  notch  of  the  housing. 

Be  sure  the  slide  is  entirely  down  before  attempting  to  fire  the  piece; 
otherwise  the  primer  may  be  blown  to  the  rear,  endangering  the  lives 
of  the  detachment. 

To  Dismount  the  Mechanism. — To  remove  the  mechanism  from  the 
spindle,  draw  the  collar  catch  to  the  rear  and  unscrew  the  hinged  collar. 

To  remove  the  slide  from  the  housing,  draw  the  slide  stop  out 
to  the  left  as  far  as  it  will  go.  The  slide  may  then  be  lifted  from  the 
housing. 

To  remove  the  firing  leaf  and  slide  catch  from  the  slide,  start  the 
split  pin  which  passes  through  the  leaf  pivot  by  pressing  it  against  the 
bench  or  other  surface  and  then  draw  it  out.  The  pivot  is  then  free 
to  be  removed,  and  its  removal  frees  the  leaf  and  slide  catch  from  the 
slide. 

The  collar  catch  may  be  removed  by  unscrewing  the  screw  at  the 
lower  edge  of  the  housing. 

The  slide  stop  may  be  removed  by  unscrewing  it  from  the  housing 
with  the  wrench  provided  for  that  purpose.  The  slide  stop  should  not 
be  removed  except  when  necessary  to  repair  it  or  to  replace  a  broken 
spring. 

The  contact-clip  housing  may  be  removed  from  the  leaf  by  unscrew- 


ARMAMENT  179 

ing  the  nut  on  the  under  side  of  the  leaf.  The  contact  clip  is  held 
to  place  in  its  housing  by  spring  pressure  only,  and  may  be  removed 
by  drawing  or  pushing  downward  after  the  cable  terminal  has  been 
removed. 

FIRING  MECHANISM  6-lNCH  R.-F.  GUN,  MODEL  OF  1903 

The  principal  parts  of  this  firing  mechanism  are  the  housing,  slide, 
firing  leaf,  ejector,  contact  clip,  and  firing  cable. 

The  housing  is  screwed  on  the  rear  end  of  the  obturator  spindle 
and  does  not  rotate  with  the  block,  due  to  the  action  of  the  spindle 
key.  A  groove  on  the  rear  face  of  the  housing  carries  the  slide,  which 
has  a  horizontal  motion  on  the  right  side  of  the  axis  of  the  gun  limited 
by  the  slide  stop. 

A  notch  on  the  under  side  of  the  slide  receives  the  rack-lock  bolt. 
The  left  end  of  the  slide  is  V-shaped,  with  the  point  of  the  V  to  the 
right.  The  point  of  the  V  is  extended  to  the  right  by  a  notch  cut 
through  the  slide.  When  the  slide  is  in  position,  breech  closed,  the 
stem  of  the  primer  passes  through  the  notch,  the  base  of  the  primer 
being  supported  by  the  body  of  the  slide. 

The  firing  leaf  is  a  vertical  lever,  pivoted  to  the  slide  by  the  firing-leaf 
pivot  and  pivot  pin.  A  horizontal  notch  is  cut  into  the  left  side  of 
the  lower  arm  of  the  firing  leaf.  The  stem  of  the  primer  passes  through 
this  notch  when  the  slide  is  in  the  firing  position. 

The  contact  clip  is  attached  to  the  firing  leaf  by  the  clip  housing 
and  housing  nut.  The  housing  is  insulated  from  the  slide  by  the  clip- 
housing  insulation.  When  the  slide  is  in  firing  position,  the  clip 
embraces  the  button  on  the  end  of  the  primer  stem,  forming  electrical 
connection  with  the  primer. 

The  firing  cable  is  connected  to  the  clip  housing  by  the  firing- 
cable  terminal,  consisting  of  a  split  pin  with  enlarged  end,  held  in 
place  by  friction.  The  other  end  of  the  firing  cable  is  similarly  attached 
to  the  firing-cable  bracket  on  the  breech  of  the  gun.  The  lower  arm 
of  the  firing  lever  lies  against  the  upper  arm  of  the  firing  leaf  when 
the  slide  is  in  firing  position.  When  the  lanyard  is  drawn  to  the  rear, 
the  lower  end  of  the  firing  lever  presses  the  upper  end  of  the  firing- 
leaf  to  the  front,  causing  the  lower  end  of  the  leaf  to  strike  the  primer 
button  and  draw  it  to  the  rear,  exploding  the  primer. 

When  the  rack  moves  to  the  right  in  opening  the  breech,  the  rack 
lock  carries  with  it  the  slide,  leaving  the  primer  free  to  be  ejected  and 
freeing  the  leaf  from  contact  with  the  firing  lever. 


180  THE  SERVICE  OF  COAST  ARTILLERY 

In  closing  the  breech  the  leaf  does  not  come  in  contact  with  the 
firing  lever  nor  the  contact  clip  embrace  the  primer  button  until  the 
rotation  of  the  block  is  practically  completed.  By  drawing  downward 
on  the  rack-lock  handle,  the  slide  is  freed  from  the  rack  and  may 
be  moved  independently,  to  permit  the  placing  of  a  primer  in  the  vent 
without  opening  the  breech. 

The  ejector  consists  of  a  horizontal  lever,  pivoted  to  the  housing 
of  the  firing  mechanism.  The  right  end  lies  in  a  groove  cut  in  the  end 
of  the  spindle.  This  end  is  forked,  the  fork  partially  surrounding 
the  mouth  of  the  vent  and  lying  in  front  of  the  rim  of  the  primer. 
The  left  end  of  the  ejector  is  broadened  to  be  struck  with  the  hand. 
The  ejector  spring,  acting  on  the  left  end  of  the  ejector,  holds  the  fork 
normally  in  its  groove  in  the  spindle.  One  side  of  this  groove  is  beveled 
to  allow  the  fork  to  ride  out  of  the  groove  in  dismounting  the  mechan- 
ism. When  the  left  end  of  the  ejector  is  struck,  the  fork  acts  on  the 
rim  of  the  primer  to  throw  the  primer  clear  of  the  vent. 

FIRING  MECHANISM,  6-lNCH  R.-F.  GUN,  MODEL  OF  1905 

The  firing  mechanism  for  this  model  of  gun  is  very  similar  to  that 
of  the  model  of  1903.  The  essential  differences  are  given  below: 

The  mechanism  consists  of  a  housing,  slide,  firing  lever,  firing  leaf, 
safety  plunger,  ejector,  and  circuit  breaker. 

The  slide  is  operated  entirely  by  hand  and  carries 'a  handle  for 
this  purpose.  The  slide  catch  holds  the  slide  in  its  firing  position. 

The  catch  consists  of  a  lever  pivoted  at  the  base  of  the  handle. 
A  hook  on  one  end  of  the  catch  engages  a  shoulder  on  the  housing. 
The  hook  is  pressed  forward  by  the  slide-catch  spring.  The  hook  is 
disengaged  from  the  shoulder  by  the  pressure  of  the  hand  on  the  other 
arm  of  the  catch  in  grasping  the  slide  handle. 

The  safety  plunger  has  a  vertical  movement  in  a  slot  cut  in  the 
spindle  key  and  extended  in  the  carrier.  The  upper  end  of  the  plunger 
carrier  is  a  stud,  which  works  in  a  groove  in  the  spindle  key  to  guide 
the  plunger  and  limit  its  downward  movement.  The  plunger  is 
pressed  downward  by  the  plunger  spring.  When  the  breech  is  fully 
closed,  the  lower  end  of  the  plunger  enters  a  notch  cut  in  the  surface 
of  the  gear  segment.  When  rotation  of  the  block  in  opening  the  breech 
begins,  the  plunger  is  forced  upward  out  of  the  notch.  The  upper  end  of 
the  plunger  now  engages  a  shoulder  on  the  firing  lever,  preventing  any 
movement  of  the  lever  until  the  breech  is  again  fully  closed. 

The    circuit-breaker    housing    is    attached  to  the   carrier  by  two 


ARMAMENT  181 

screws.  Two  contact  pins  pass  vertically  through  the  housing  and 
are  held  in  place  by  the  contact-pin  nuts  screwed  on  their  lower  ends. 
The  circuit-breaker  is  arranged  so  that  when  the  breech  is  closed, 
the  contact  plungers  are  carried  by  the  operating  lever  under  the 
contact  pins,  thus  completing  the  firing  circuit  only  when  the  breech 
is  fully  closed. 


FIRING  MECHANISM,  G-INCH  R.-F.  GUN,  MODEL  OF  1897  Mi;   AND  5-lNCH 
R.-F.  GUN,  MODEL  OF  1897 

This  mechanism  is  intended  for  use  with  a  combination  electric 
and  friction  primer.  It  consists  of  the  following  principal  parts: 
Slide,  slide  housing,  ejector,  firing  leaf,  contact-clip,  firing  cable,  circuit 
breaker  and  safety  bar. 

The  housing  is  attached  to  the  rear  end  of  the  spindle  by  means  of 
an  interrupted  screw  thread  and  is  secured  in  place  by  a  spline  screw. 

The  slide  has  a  vertical  movement  in  guides  which  project  from  the 
rear  portion  of  the  housing,  and  its  movement  is  limited  by  the  slide 
stop,  which  has  a  horizontal  movement  in  a  slot  cut  in  the  housing, 
its  inner  end  projecting  into  a  groove  in  the  side  of  the  slide.  The 
slide  stop  is  pressed  inward  by  a  helical  spring. 

The  firing  leaf  is  pivoted  at  its  upper  end  to  the  slide  against  which 
it  lies  flat  when  in  its  normal  position. 

A  notch  is  cut  through  both  the  slide  and  the  leaf,  so  that  when 
in  its  lowered  position  the  slide  supports  the  head  of  the  primer  against 
the  pressure  of  the  powder  gases,  while  allowing  the  primer  wire  to 
extend  through  the  notch. 

When  the  leaf  is  swung  to  the  rear,  its  rear  face  catches  the  button 
at  the  end  of  the  primer  wire  and  explodes  the  primer. 

The  contact  clip  makes  electrical  connection  with  the  primer  by 
bearing  against  the  button  on  end  of  primer  wire  when  the  slide  is 
in  its  lowered  position.  The  contact  clip  is  held  in  a  housing  which 
is  secured  to  the  firing  leaf  by  the  housing  nut  and  is  insulated  from 
the  leaf  by  the  housing  insulation. 

One  end  of  the  firing  cable  is  attached  to  the  clip  housing  by  the 
firing-cable  terminal,  consisting  of  a  split  pin  with  enlarged  end  held 
in  place  by  friction,  the  other  end  attached  to  the  circuit-breaker 
contact  piece. 

The  circuit-breaker  contact  piece  is  secured  to  the  outside  of  the 
gear  segment  by  two  screws  and  insulated  therefrom.  When  the  block 
is  rotated  in  closing,  the  circuit-breaker  contact  piece  comes  into 


182  THE  SERVICE  OF  COAST  ARTILLERY 

contact  with  the  circuit-breaker  contact  pin,  making  electrical  connec- 
tion with  one  of  the  firing  leads. 

The  circuit-breaker  contact  pin  and  spring  are  inclosed  in  a  housing 
which  is  attached  to  the  block  carrier  by  two  screws  and  insulated 
therefrom.  The  pin  is  held  against  the  contact  piece  by  the  pressure 
of  its  spring.  The  end  of  the  firing  lead  is  secured  to  the  circuit-breaker 
housing  by  a  fork.  The  firing  lead  is  held  in  place  by  the  cable  clamp 
screwed  to  the  block  carrier. 

The  ejector  consists  of  a  horizontal  and  a  vertical  branch  with 
two  trunnions  near  the  angle.  It  is  supported  in  the  housing  by  these 
trunnions,  and  in  its  normal  position,  the  lower  branch,  which  is  in  the 
form  of  a  fork,  hangs  vertically  over  the  mouth  of  the  primer  seat, 
engaging  the  rim  of  the  primer  on  two  sides.  The  horizontal  branch 
projects  to  the  rear  into  a  recess  cut  in  the  front  face  of  the  slide.  The 
lower  end  of  this  recess  is  a  cam  surface.  When  the  slide  is  raised, 
this  cam  surface  forces  the  horizontal  branch  upward,  ejecting  the  primer. 
When  the  slide  is  lowered,  the  ejector  drops  into  position  against 
the  mouth  of  the  primer  seat. 

The  safety  bar  is  a  lever  pivoted  in  the  slide  housing  and  actuated 
by  a  stud  on  the  gear  segment  working  in  a  slot  cut  through  the  outer 
end  of  the  safety  bar.  At  the  beginning  of  rotation  of  the  block  in 
opening  the  breech  the  inner  end  of  the  safety  bar  rotates  inward, 
entering  a  slot  in  the  right  side  of  the  firing  leaf,  thus  preventing  any 
movement  of  the  firing  leaf,  except  when  the  breech  is  fully  closed. 

To  Dismount  Mechanism. — Open  the  breech.  Unscrew  safety-bar 
pivot  and  remove  safety  bar.  Detach  firing  cable  from  circuit-breaker 
contact  piece.  Pull  outward  on  slide  stop  and  lift  slide  from  housing. 
Unscrew  housing  spline  screw  and  revolve  housing  90  degrees  to  the 
right,  when  the  housing  may  be  drawn  to  the  rear  from  the  spindle. 
Unscrew  the  spindle  nut  and  the  spindle-key  screw,  and  remove  the 
spindle  key. 

Be  careful  not  to  remove  spindle  nut  and  spindle  key  before  opening 
the  breech,  as  in  that  case  the  split  rings  are  liable  to  drop  down  and 
prevent  the  withdrawal  of  the  block. 

The  spindle,  split  rings,  pad,  etc.,  are  then  free  to  be  removed 
from  the  block. 

Take  out  the  two  gear-segment  screws  and  drive  off  the  gear 
segment,  using  a  copper  drift  to  prevent  injury  to  the  gear  segment. 

Take  out  the  latch-lever  pivot  and  remove  the  latch  lever,  spring, 
and  bolt.  The  block  is  then  free  to  be  removed  from  the  carrier. 
Drive  out  the  pivot  pin  and  remove  the  pivot  nut,  unscrew  the  pivot, 


ARMAMENT  183 

and  the  pinion  and  lever  are  then  free  to  be  removed  from  the  carrier. 
Drive  out  the  hinge  pin,  being  careful  to  support  the  carrier  while 
doing  so,  and  the  carrier  is  then  free  from  the  piece. 

FIRING  MECHANISM,  5-lNCH  R.-F.  GUN,  MODEL  OF  1900 

This  mechanism  is  practically  the  same  as  used  in  the  model  1897, 
except  as  follows:  The  housing  of  this  mechanism  is  attached  to  the 
spindle  by  means  of  a  yoke.  The  firing  mechanism  turns  with  the 
block  during  rotation.  The  safety  lever  lies  in  a  groove  in  the  surface 
of  the  guide  cylinder. 

A  projection  on  the  front  end  of  the  safety  lever  rides  in  a  groove 
cut  in  the  block  carrier.  When  the  breech  is  fully  closed,  this  projection 
enters  a  well  cut  at  the  end  of  the  groove  in  the  block  carrier,  allowing 
the  hook  on  the  rear  end  of  the  safety  lever  to  drop  and  free  the  firing 
leaf.  At  the  beginning  of  rotation  of  the  block  in  opening  the  breech 
the  safety-lever  hook  rises  and  prevents  any  movement  of  the  firing 
leaf. 

ADJUSTING  GAS-CHECK  PADS 

Experience  has  shown  that,  as  a  rule,  gas-check  pads  are  too 
tight.  It  has  been  customary,  because  of  the  simplicity  of  the  method, 
to  adjust  the  pad  with  the  breech  open  by  tightening  the  spindle  nut 
until  the  pad  could  just  be  turned  by  hand.  In  cold  weather  when  the 
pad  is  relatively  rigid  this  adjustment  is  satisfactory;  in  warm  weather, 
however,  the  pad  being  more  plastic  is  forced  outward  readily  till  it 
extends  beyond  the  surface  of  the  split  rings.  When  this  occurs,  even 
though  the  pad  can  be  turned  by  hand,  the  pad  is  not  in  proper  adjust- 
ment, since  when  forced  into  its  seat  it  will  be  pressed  over  the  rear 
ring  and  injured.  As  the  object  of  the  pad  is  to  form  a  perfect  gas 
check  at  the  rear  of  the  tube,  the  best  adjustment  is  made  with  the 
pad  seated. 

To  Adjust  Pads, — Close  the  breech,  having  the  spindle  nut  loose, 
but  not  so  loose  as  to  permit  slipping  of  the  pad  or  split  rings;  rotate 
the  block  until  one-half  of  the  rotation  has  been  accomplished.  With 
the  mechanism  in  position,  screw  up  the  spindle  nut  as  tight  as  it  can 
be  screwed  with  the  wrenches  provided. 

With  the  new  spindle  nut,  having  a  locking  device,  it  is  necessary 
to  insert  the  end  of  a  screw-driver  in  the  opening  of  the  nut  in  order  to 
spread  it  sufficiently  to  allow  its  rotation  without  rotating  the  spindle. 


184 


THE  SERVICE  OF  COAST  ARTILLERY 


Lock  the  spindle  nut  and  rotate  the  breechblock  until  the  breech 
is  completely  closed.  This  last  operation  presses  the  pad  in  its  seat, 
due  to  the  forward  motion  of  the  block. 

The  pad  is  now  in  proper  adjustment  for  firing. 


GUN 


ID 


REAR  ADAPTER  FRONT  ADAPTER 

ADAPTER  CLAMP  WEDGE 


LOCATING  GAUGE 


BRISTLE  SPONGE 


SPONGE  ROD 


1=3 


HANDSPIKE 


ADJUSTING  WRENCH  FOR  M.  1888-1895 


n 


CLAMPING  WRENCH 


U 


HAND  EXTRACTOR 


VENT  CLEANER 


OIL  CAN 


CLIP  EXTRACTOR 


SPINDLE  PLATE  SCREW  WRENCH     SECURING  SCREWS 


L_\ 


FIG.  17. 


THE  1-POUNDER  AND  2.95-INCH  SUBCALIBER   GUNS 

As  the  name  implies,  the  subcaliber  tube  is  in  reality  a  gun  of  lesser 
caliber  than  the  gun  in  which  used.  It  is  inserted  into  the  bores  of 
seacoast  cannon  for  the  purpose  of  providing  a  means  of  practicing 


ARMAMENT 


185 


in  firings  with  these  guns  under  conditions  resembling  those  of  service 
practice,  the  difference  being  that  the  projectile  of  the  subcaliber 
gun  is  of  much  smaller  caliber  when  compared  to  the  bore  of  the  larger 
gun. 

The  principal  parts  of  a  type  of  subcaliber  tube  are  shown  in  detail 
in  Fig.  17. 

A  statement  of  the  various  sizes  of  tubes  provided  for  use  in  sea- 
coast  cannon,  as  well  as  the  interehangeability  of  the  same,  is  given 
in  the  following  table: 


INTERCHANGEABILITY    OF   SUBCALIBEK   GUNS. 


Subcaliber 

of  1900. 
Subcaliber 

of  1900, 
Subcaliber 

of  1888. 
Subcaliber 

of  1888, 
Subcaliber 

of  1888, 


guns  for  5-inch  guns,  model 

guns  for  6-inch  guns,  models 

1903,  and  1905. 

guns  for  8-inch  guns,  model 

guns  for  10-inch  guns,  models 
1895,  and  1900. 
guns  for  12-inch  guns,  models 
1895,  and  1900. 


*  Subcaliber    guns    for    4-inch    Driggs- 

Schroeder  guns. 

*  Subcaliber  guns  for  5-inch  guns,  model 

of  1897. 


*  Subcaliber  guns  for  6-inch  guns,  model 
of  1897. 


Subcaliber  guns  for  4.72-inch  and  6-inch 
Armstrong  guns. 


Are  interchangeable ;  that  is,  these  guns 
will  all  fit  into  the  5-inch  guns,  model 
of  1900;  6-inch  guns,  models  of  1900, 
1903  and  1905;  and  8-,  10-,  and  12- 
inch  guns  of  all  models  when  fitted 
with  the  proper  adapters. 

They  will  not  fit  in  the  4-inch  Driggs- 
Schroeder  5-inch  and  6-inch  guns, 
model  of  1897,  and  4.72-inch  and 
6-inch  Armstrong  guns,  as  these  guns 
must  have  subcaliber  guns  fitted  with 
special  rear  adapters  forming  a  per- 
manent part  of  the  subcaliber  gun. 

Are  interchangeable  in  4-inch  Driggs- 
Schroeder  guns,  and  8-,  10-,  and  12- 
inch  guns  of  all  models  when  fitted 
with  the  proper  adapters. 

Are  interchangeable  in  5-inch  guns, 
model  of  1897,  and  8-,  10-,  and  12-inch 
guns  of  all  models  when  fitted  with 
the  proper  adapters. 

Are  interchangeable  in  6-inch  guns, 
model  of  1897,  and  10-  and  12-inch 
guns  of  all  models  when  fitted  with 
the  proper  adapters. 

Are  interchangeable,  respectively,  in  all 
4.72-inch  and  6-inch  Armstrong  guns, 
and  10-  and  12-inch  guns  of  all  models 
when  fitted  wtih  the  proper  adapters. 


*  The  4-inch  Driggs-Schroeder,  6-inch  1897,  and  6-inch  Armstrong  subcaliber 
guns  should  have  adjusting  wrench  holes,  if  not  already  provided,  drilled  in  the 
breech  face,  if  these  guns  are  ever  mounted  in  10-  or  12-inch  guns. 

Each  caliber  and  model  of  gun  requires  a  special  adapter  which  can  not  be  used 
in  any  other  model  of  gun. 

The  2.95-inch  subcaliber  guns  for  12-inch  mortars,  model  of  1886,  are  not  inter- 
changeable with  those  for  12-inch  mortars,  model  of  1890. 

The  directions  for  assembling  and  using  the  tubes  are  practically 
the  same  for  all  guns,  so  that  an  explanation  of  the  1 -pounder  sub- 
caliber  tube  used  in  the  bores  of  8-,  10-,  and  12-inch  B.-L.  Rifles  will 
serve  as  a  guide: 


186  THE  SERVICE  OF  COAST  ARTILLERY 

To  Assemble  the  Tube. — First  see  that  the  chamber  and  bore  of 
the  subcaliber  gun,  and  of  the  gun  itself,  are  perfectly  clean.  Remove 
the  blank  pressure  plugs  from  the  mushroom  head  and  put  on  the 
obturator  spindle  plate  with  its  two  screws.  This  is  done  by  using 
the  securing  screw  wrench.  The  screw  heads  should  be  tightened  well 
upon  the  plate.  Then  insert  the  loading  tray  to  prevent  injuring 
the  adapters  on  the  breech  threads. 

The  subcaliber  gun  with  its  adapters  should  now  be  inserted  into  the 
chamber  of  the  large  gun  by  pushing  it  forward  with  a  handspike 
sufficiently  far  to  cause  the  front  adapter  to  seat  fir-mly  in  the  slope 
of  the  powder  chamber.  It  is  tapered  so  that  it  will  fit  this  slope. 
With  the  10- and  12-inch  rifles,  model  of  1900,  the  subcaliber  gun  should 
be  supported  with  a  handspike  while  the  bronze  shoe  is  slipped  under 
the  rear  adapter. 

When  the  subcaliber  gun  is  as  far  forward  as  it  can  go  remove 
the  handspike  and  insert  locating  gauge  in  the  chamber  of  the  sub- 
caliber  gun  with  its  flange  pulled  to  the  rear.  Then  completely  close 
the  breech  of  the  large  gun  and  open  it  again  and  note  whether  the 
flange  of  the  locating  gauge  is  flush  with  the  face  of  the  subcaliber  gun. 
If  the  gauge  protrudes  revolve  the  subcaliber  gun  left-handed.  If 
below  the  face  of  the  subcaliber  gun  turn  the  gun  right-haniled.  One 
complete  turn  of  the  gun  will  make  a  difference  in  the  distance  from 
the  face  of  the  subcaliber  gun  to  the  mushroom  head  of  1/10  of  an  inch. 
This  adjustment  is  made  with  the  adjusting  wrench,  having  its  lugs 
entered  into  the  holes  in  the  rear  face  of  the  gun. 

The  subcaliber  gun  should  be  adjusted  in  this  manner  until  the 
flange  of  the  locating  gauge  is  brought  exactly  flush  wiien  the  breech 
is  closed.  The  thread  clamp  screw  should  be  tightened  with  the 
clamping  wrench  so  that  the  subcaliber  gun  will  be  prevented  from 
turning.  The  gun  is  then  ready  for  firing. 

To  Use  the  Subcaliber  Gun. — Insert  a  subcaliber  cartridge,  close 
the  breech  and  fire  as  with  the  regular  ammunition.  The  breech  is 
then  opened,  the  empty  cartridge  case  removed  after  each  round 
with  the  hand  extractor.  Should  a  cartridge  case  stick  so  that  it  can 
not  be  removed  with  the  hand  extractor,  use  the  clip  extractor,  which 
is  provided  for  such  emergencies.  It  may  be  necessary  to  pass  a  light 
rope  through  the  eye  of  the  clip  extractor  in  order  to  apply  greater 
force  against  the  face  of  the  breech. 

To  Dismount  the  Tube. — Insert  the  loading  tray  and  loosen  up 
both  clamp  screws.  Then  insert  the  handspike,  leaving  same  to  support 
the  weight,  and  remove  the  adapter  shoe.  Then  pull  the  subcaliber 


ARMAMENT  187 

gun  to  the  rear  and  out.  Should  the  gun  stick  attach  a  rope  over  the 
enlargement  of  the  breech  and  pull  out,  being  careful  that  the  gun  does 
not  come  to  the  rear  too  rapidly  after  being  released. 

It  is  important  that  the  subcaliber  gun  be  Unloaded  and  then 
loosened  before  the  adapter  shoe  is  removed  from  under  the  rear 
adapter,  because  if  the  shoe  is  removed  before  the  gun  is  loosened 
the  lowering  of  the  breech  of  the  subcaliber  gun  will  cause  the  front 
adapter  to  bind  in  its  seat  and  considerable  difficulty  will  be  had  in 
removing  the  tube.  Care  should  be  taken  in  assembling  and  dis- 
mounting in  order  to  prevent  the  turning  surfaces  of  the  adapters 
from  striking  the  threads  of  the  breech  recess  or  any  other  hard  sub- 
stance and  burring  them.  Care  should  also  be  taken  in  loading  not 
to  drive  the  point  of  the  shell  against  the  edge  of  the  chamber  of  the 
subcaliber  gun.  Both  guns  should  be  thoroughly  cleaned  and  oiled 
after  firing. 

CARRIAGES    FOR    COAST    ARTILLERY    CANNON 

The  method  of  mounting  seacoast  guns  determines  the  design  of 
emplacements.  Conversely,  the  design  of  emplacements  also  has 
a  bearing  upon  the  suitability  of  mounts  for  guns.  It  is  evident  that 
the  principal  object  of  an  emplacement  is  to  provide  a  firm,  unyielding 
support  for  the  gun  and  carriage,  so  that  the  gun  may  be  loaded, 
manipulated  and  fired  under  conditions  giving  the  greatest  protection  to 
the  personnel  and  armament  from  the  fire  of  the  enemy. 

Elements  influencing  the  selection  of  type  of  carriage  may  be  briefly 
stated  as  follows: 

1.  Rapidity  of    Fire. — With  large  guns  (10-  and  12-inch  calibers) 
greater  rapidity  of  fire  is  undoubtedly  obtained  with  the  disappearing 
type  of  carriage.     The  advantage  in  time  and  less  fatigue  of  men  are  such 
as  to  give  a  decided  preference  for  the  disappearing  mount.     When 
the  caliber  of  the  gun  is  six  inches  or  less  the  advantage  obtained  by 
the  use  of  the  disappearing  type  of  carriage  may  be  considered  as  nil, 
and   for   calibers  less  than  six   inches  the  non-disappearing  type   is 
decidedly  preferable. 

2.  Exposure  of  Gun,  Carriage,  or  Mount. — With  the  non-disappear- 
ing carriage  without  a  shield,  substantially  every  man  working  at  the 
gun,  except  those  on  the  elevating  cranks,  is  exposed  to  direct  fire; 
while  with  the  disappearing  carriage  and  direct  laying  (Case  I  and  II) 
only  one  man  is  exposed.     In  indirect  laying  (Case  III)  none  of  the 
personnel  are  exposed  for  small  angles  of  fall. 


188  THE  SERVICE  OF  COAST  ARTILLERY 

Considering  the  non-disappearing  type  of  carriage  illustrated  by 
the  Armstrong  Pedestal  Mount  with  shield,  it  may  be  stated  that  the 
gunner  has  better  protection  than  with  any  other  type  of  mount. 
The  gun,  however,  on  a  non-disappearing  carriage  is  exposed  at  all 
times;  while  with  the  disappearing  type  it  is  only  exposed,  in  direct 
laying,  for  the  few  seconds  required  for  aiming;  and  for  indirect  laying 
it  is  exposed  for  even  a  shorter  time,  that  is,  while  the  piece  is  actually 
being  fired. 

The  damage,  caused  by  a  shot  hitting  the  disappearing  type  of 
carriage,  when  exposed  to  the  direct  fire  of  the  enemy,  is  more  apt 
to  be  greater  and  more  serious  than  the  damage,  from  the  same  shot, 
to  the  non-disappearing  type;  due  to  the  numerous  additional  devices 
required  in  the  former  type. 

Carriages  for  coast  artillery  cannon  are  classified  as  follows: 

1.  According  to  the  nature  of  the  cover  afforded  by  the  emplace- 
ments, into: 

Barbette  (Barbette  Proper,  Pedestal  Mount,  Special  Mounts), 

Disappearing, 

Masking  Mount, 

Casemate, 

Mortar. 

2.  According  to  the  axis  of  rotation  about  which  they  are  traversed, 
into: 

Front  Pintle, 
Center  Pintle. 

3.  According  to  the  area  of  fire  covered  by  them,  into: 

Limited  Fire, 
All-around  Fire. 

BARBETTE 

Barbette  Proper. — This  class  of  carriage  includes  the  non-dis- 
appearing types,  with  guns  that  remain  above  the  parapet  for  loading 
and  firing.  Carriages  of  this  type  may  be  either  front  pintle  or  center 
pintle,  limited  fire,  or  all-around  fire.  A  type  of  this  class  of  carriage 
is  illustrated  in  the  12-inch  barbette  carriage  shown  in  Plate  XVIII. 
The  carriage  is  of  the  center  pintle  form  and  consists  essentially  of  the 
following  parts:  A  base  ring  resting  upon  the  masonry  platform,  a 
traversing  roller  ring,  a  combined  racer  and  chassis,  and  a  top  carriage 
containing  the  trunnion  beds  and  the  recoil  cylinders. 

The  base  ring  is  of  cast  iron,  in  one  piece,  10  feet  8  inches  in 
diameter,  secured  to  the  platform  by  sixteen  2-inch  bolts  through 


ARMAMENT  189 

the  flange.  The  lower  roller  path,  with  an  outside  diameter  of  96.7 
inches,  is  on  its  upper  surface. 

The  pintle  rising  from  the  center  of  the  base  ring  is  a  right 
cylinder,  8.05  inches  high  and  37.97  inches  in  diameter,  with  an  oil 
groove  on  its  outer  surface.  Upon  the  lower  roller  path  rests  a  circle 
of  twenty  forged-steel  conical  rollers  securely  held  in  place  by  two 
concentric  distance  rings.  The  distance  rings  are  kept  concentric 
by  ten  separators,  bolted  between  them,  and  the  system  is  held  con- 
centric with  the  pintle  by  flanges  on  the  inner  ends  of  the  rollers. 

The  combined  racer  and  chassis  is  of  cast  iron,  made  in  one  piece, 
with  transoms  and  inner  and  outer  strengthening  ribs.  The  lower 
surface,  constituting  the  upper  roller  path,  rests  upon  the  traversing 
roller-ring  system.  Four  forged-steel  clips  are  bolted  to  its  lower 
exterior  surface  with  five  If-inch  tap  bolts.  The  lips  of  these  clips 
engage  under  a  corresponding  flange  on  the  base  ring.  Between  these 
clips  is  a  dust  guard,  in  four  sections,  extending  around  the  traversing 
roller-ring  system.  A  circular  flange  on  the  interior  of  the  racer 
constitutes  the  pintle  ring,  and  extends  down  over  the  pintle  on  the 
base  ring. 

The  top  carriage  rests  upon  eight  steel  rollers,  8  inches  in  diameter, 
mounted  on  a  U-shaped  recess  in  the  top  of  the  chassis  rails.  These 
rollers  are  bushed  with  bronze  and  mounted  upon  2-inch  screw  axles 
seated  in  the  walls  of  the  recess.  The  chassis  rails  have  an  inclination 
upwards  and  to  the  rear,  of  four  degrees,  and  are  strengthened  by 
three  transoms.  The  piston  rods  pass  through  lugs  which  project 
upwards  from  the  front  ends  of  the  rails  and  are  secured  by  the  piston- 
rod  nuts  and  check  nuts.  The  front  surface  of  these  lugs  and  of 
the  rails  is  planed  as  a  seat  for  a  shield  to  protect  the  gu  ners. 

The  top  carriage  h  of  steel,  cast  in  one  pi  ce.  It  consists  of  the 
two  trunnion  bed  side  frames  in  which  are  cast  the  two  recoil 
cylinders  united  by  a  transom  passing  under  the  gun. 

Flanges  upon  the  recoil  cylinder  are  clipped  over  corresponding 
flanges  on  the  chassis  rails.  The  cylinders  are  8^  inches  in  interior 
diameter,  fitted  each  with  a  piston  rod  3i  inches  in  diameter,  having 
a  piston  with  a  clearance  of  0.1  of  an  inch  all  around.  During  the 
recoil  the  pistons  remain  stationary,  and  the  top  carriage  with  the 
recoil  cylinders  is  drawn  over  them.  Uniform  resistance  in  the 
cylinders  is  obtained  by  the  passage  of  the  liquid  from  front  to  rear, 
through  varying  orifices  caused  by  throttling  bars  whose  inner  faces 
are  curved.  There  are  two  throttling  bars  in  each  cylinder,  and  each 
piston  has  rectangular  slots,  one  on  each  side,  which  fit  over  thorn. 


190  THE  SERVICE  OF  COAST  ARTILLERY 

The  sectional  areas  of  these  bars  are  such  that  the  orifices  for  the 
flow  of  liquid  vary  with  the  position  of  the  piston  during  recoil  so 
as  to  obtain  the  desired  resistance  in  the  cylinder.  The  energy  of 
recoil  is  taken  up  by  the  resistance  which  the  fluid  offers  to  being 
driven  through  the  orifices. 

After  recoiling,  the  gun  returns  to  the  firing  position  by  the 
action  of  gravity,  the  slope  of  the  chassis  rails  being  sufficient  to 
permit  the  top  carriage  to  move  forward  on  the  rollers.  The  rear 
end  of  each  cylinder  is  closed  by  a  screw  plug-cover  which  has  in 
its  front  face  a  cylindrical  cavity  5  inches  deep  with  rounded  bottom, 
and  the  end  of  the  piston  rod  fits  into  this  cavity  writh  a  clearance 
of  .0075  of  an  inch  on  the  diameter.  When  the  gun  returns  to  the 
firing  position  the  liquid  caught  in  the  cavity  can  only  escape  by 
the  small  clearance,  thus  acting  as  a  buffer  to  check  the  velocity  at 
the  end  of  the  return  into  battery.  At  the  front  end  of  the  recoil 
cylinder  there  are  the  usual  stuffing  boxes,  with  glands  and  fol- 
lowers. 

A  copper  equalizing  pipe  entering  immediately  behind  the  glands 
connects  the  front  ends  of  the  cylinders.  By  this  means  the  pressure 
in  both  cylinders  is  always  the  same.  The  recoil  should  be  about 
40  inches. 

The  cylinders  are  provided  with  filling  and  emptying  plugs  suitably 
placed. 

The  cap  squares  are  dovetailed  and  secured  by  two  1-inch  tap 
bolts. 

The  carriage  is  traversed  by  a  chain,  coupled  through  its  end 
links  to  two  ear  bolts  passing  through  lugs  cast  on  the  outer  vertical 
surface  of  the  base  ring  below  the  roller  path.  By  means  of  nuts 
on  these  bolts  the  length  of  the  chain  may  be  given  all  necessary 
adjustment. 

Wrought-iron  bolts  are  mounted  vertically  8  inches  each  side  of 
the  longitudinal  axial  (plane)  bolted  upon  a  racer.  A  rectangular 
slot  is  mortised  through  the  lower  end  of  these  bolts,  in  the  walls 
of  which  are  mounted  1^-inch  steel  bolts  which  serve  as  axles  for 
pulleys  for  changing  the  direction  of  the  traversing  chain,  to  carry 
it  up  over  a  sprocket  wheel  splined  to  a  worm  gear  in  front  of  it. 
This  sprocket  wheel  and  worm  gear  are  mounted  on  a  horizontal 
steel  axle  bolt  in  a  bearing  cast  on  the  racer. 

The  traversing  worm  gear  engages  in  a  worm  keyed  on  a  transverse 
through  shaft,  mounted  in  bronze  bush  bearings  in  brackets  cast 
on  and  projecting  to  the  front  from  the  chassis  rails.  On  the  squared 


ARMAMENT  191 

ends  of  the  traversing  shaft  there  are  crank  levers  IS  inches  long, 
with  handles  covered  with  loose  brass  sleeves. 

Pointing  in  elevation  is  given  by  a  rack,  bolted  by  two  l|-inch 
bolts  to  the  elevating  band  on  the  gun.  A  pinion,  mounted  upon 
a  short  cross  shaft,  engages  in  the  rack.  This  elevating  pinion  shaft 
is  mounted  in  a  bearing  drilled  in  the  top  carriage  over  the  rear  end 
of  the  right-recoil  cylinder.  On  the  outer  end  of  the  same  shaft 
there  is  keyed  a  friction  clutch  disk,  fitting  in  a  ground  seat  in  the 
outer  face  of  the  worm  gear,  and  is  brought  to  a  bearing  in  its  seat 
by  a  nut  on  the  end  of  the  shaft.  By  this  clutch  excessive  stress  on 
the  elevating  system  is  relieved  during  firing. 

This  worm  gear  engages  in  a  worm  splined  upon  a  vertical  shaft 
having  its  bearings  in  two  lugs  on  the  outside  of  the  top  carriage. 
On  the  lower  end  of  this  worm  shaft  there  is  splined  a  bevel  gear 
which  takes  in  a  second  bevel  gear  upon  the  main  elevating  shaft; 
this  is  supported,  parallel  to  the  top  surface  of  the  right  chassis 
rail,  by  the  two  wrought-iron  brackets  bolted  to  the  outer  face  of 
the  latter.  This  second  bevel  gear  slides  upon  the  squared  section 
of  this  shaft,  being  carried  back  and  forth  in  the  recoil  of  the  top 
carriage  by  an  arm  cast  upon  the  latter,  through  which  the  hub  of 
the  gear  extends,  secured  by  a  nut  abutting  against  the  front  side 
of  the  arm.  There  is  a  hand  wheel  on  the  rear  end  of  the  shaft  for 
the  use  of  the  gunners.  The  front  end  has  anothe  •  bevel  gear  mounted 
thereon,  which  engages  in  a  bevel  gear  mounted  on  a  transverse 
through  shaft,  having  its  bearings  in  bronze  sleeves,  bolted  to  the 
chassis  rails,  near  their  forward  ends,  as  bushings  of  holes  drilled 
in  the  same.  On  each  end  of  this  shaft  there  is  a  bronze  handwheel 
to  assist  in  elevating  the  gun. 

For  the  shot  hoist  there  is  a  through  shaft  journaled  in  the  rear 
ends  of  the  chassis  rails  above  the  upper  roller  path,  with  a  bronze 
bushed  middle  bearing  in  the  lug  projecting  from  the  rear  transom. 
This  shaft  is  held  against  lateral  motion  by  a  collar  on  the  outside 
of  each  chassis  rail.  A  bevel  gear  keyed  upon  this  shaft  under  the 
right  chassis  rail  takes  in  a  bevel  gear  splined  on  the  lower  end  of 
the  vertical  shaft  journaled  in  two  other  lugs  extending  from  the 
rear  transom.  Above  this  latter  gear  there  is  a  worm  splined  on  this 
same  vertical  shaft,  which  worm  takes  in  a  segment  of  a  worm  wheel 
keyed  upon  a  second  shaft  called  the  shot-hoist  shaft,  parallel  to 
the  first  through  shaft.  The  bearings  of  this  last  shaft  are  in 
brackets  extending  to  the  rear  from  the  chassis  side  frames,  and 
cast  in  one  piece  with  them. 


192  THE  SERVICE  OF  COAST  ARTILLERY 

A  lever  mounted  upon  a  squared  section  of  this  second  shaft, 
terminating  in  a  fork  with  slotted  ends,  is'  designed  to  receive  the 
trunnions  of  the  projectile  tray,  support  being  given  lower  down  on 
the  tray  by  a  third  arm  projecting  below  the  fork.  Power  is  applied 
to  the  crank  levers  on  each  end  of  the  first  shaft.  By  the  rotation 
of  these  cranks  the  tray,  with  its  projectile,  is  lifted  to  the  position 
for  ramming.  The  handles  of  these  levers  are  covered  with  loose 
brass  sleeves. 

The  shot  is  brought  to  the  gun  in  a  tray,  resting  upon  a  three- 
wheeled  truck  or  shot  barrel,  consisting  of  a  body,  two  cast-iron 
14-inch  truck  wheels,  mounted  on  a  wrought-iron  axle,  and  a  cast- 
iron  5-inch  caster  wheel,  mounted  in  a  wrought-iron  fork. 

The  loading  platform  consists  of  a  flooring  45  inches  above  the 
terreplin,  supported  by  boiler -iron  brackets  strengthened  by  T  irons 
riveted  along  the  edges.  It  is  inclosed  by  a  wrought-iron  tubing 
rail.  A  set  of  four  straps  on  each  side  gives  access  to  the  platform. 
These  are  supported  by  side  pieces  and  struts  bolted  to  the  plat- 
form. A  slot  through  the  middle  of  the  flooring  permits  the  shot 
to  be  lifted  by  the  hoist  to  its  position  opposite  the  breech  of  the 
gun,  into  which  it  is  pushed  and  rammed  by  cannoneers  standing  on 
the  platform.  A  separate  loading  tray  is  placed  in  the  gun  to  protect 
the  threads. 

The  carriage  permits  of  the  gun  being  traversed  through  320 
degrees,  and  elevated  from  minus  7  degrees  to  plus  18  degrees. 

The  cylinders  should  be  filled  with  neutral  oil  before  firing. 

Pedestal  Mount  (see  Plate  XVII). — The  pedestal  mount  or  carriage 
is  one  of  the  barbette  class  well  illustrated  by  the  15-pdr.  barbette 
carriage,  model  of  1903,  which  consists  of  a  pedestal,  pivot  yoke, 
cradle,  traversing  and  loading  mechanism,  shield,  shield  supports, 
and  shoulder  rests,  with  the  necessary  peep  and  telescopic  sights, 
firing  mechanism,  and  electrical  attachments. 

Pedestal. — The  pedestal  is  made  of  cast  steel,  and  has  the  general 
form  of  the  frustum  of  a  cone  united  at  its  top  to  a  cylindrical 
section  and  at  its  bottom  to  a  base,  in  the  flange  of  which  are 
drilled  holes  for  the  fourteen  foundation  bolts  and  three  leveling 
screws.  Two  hand-holes  covered  with  water-tight  plates  are  pro- 
vided for  cleaning  the  interior.  The  joints  of  the  covers  are  made 
water-tight  by  means  of  Garlock's  gasket  packing.  There  are  twelve 
holes  equally  spaced  for  the  foundation  bolts,  and  two  extra  holes 
drilled  so  as  to  enable  the  use  of  this  pedestal  in  emplacements  of 
the  15-pounder  barbette  carriage,  model  of  1902. 


ARMAMENT  193 

The  exterior  of  the  cylindrical  part  is  finished  and  forms  a  seat 
for  the  traversing  worm  wheel.  Beneath  this  seat  on  the  front  of 
the  pedestal  is  a  boss  to  which  the  friction  band  is  secured  by  a 
stud  bolt.  An  annular  boss  is  cast  in  the  bottom  of  the  pedestal. 
This  boss  is  bushed  with  bronze  and  forms  a  bearing  for  the  lower 
end  of  the  pivot  yoke.  The  upper  interior  cylindrical  part  of  the 
pedestal  is  also  bushed  with  a  bronze  bearing.  These  two  bearings 
serve  to  keep  the  pivot  yoke  in  a  vertical  position.  The  weight  of 
the  revolving  parts  is  supported  by  a  ball  thrust  bearing  inserted 
between  the  end  of  the  pivot  yoke  and  the  bottom  of  the  cylindrical 
recess  formed  by  the  annular  boss  at  the  bottom  of  the  base  of  the 
pedestal. 

Pivot  Yoke. — The  pivot  yoke  is  of  cast  steel,  and  has  a  cored 
conical  stem  from  which  rise  two  vertical  cheeks.  In  the  cheeks 
are  bronze-lined  trunnion  beds  for  the  trunnions  of  the  cradle.  These 
beds  are  fitted  with  interchangeable  dovetailed  cap  squares  bolted 
to  the  cheeks.  Finished  recesses  are  formed  in  the  outer  faces  of 
the  cheeks  of  the  pivot  yoke  into  which  the  shield  supports  are  fitted 
and  bolted.  There  is  an  annular  projection  under  the  cheeks  of 
the  pivot  yoke  to  which  is  bolted  a  cover  to  protect  the  traversing 
worm  wheel.  The  cored  holes  in  the  stem  of  the  pivot  yoke  are 
closed  with  plugs  to  prevent  the  entry  of  water  into  the  bearings 
of  the  pedestal.  The  rear  faces  of  the  cheeks  are  finished  so  as  to 
receive  a  bracket  containing  the  traversing  and  elevating  mechan- 
isms. This  bracket  is  bolted  to  the  rear  faces  of  the  cheeks  by  six 
bolts.  There  are  four  oil  holes  provided  in  the  pivot  yoke  for  oiling 
its  upper  bearings  in  the  pedestal,  and  an  oil  pipe  leading  from  a 
fifth  hole  to  the  thrust  bearing  through  the  cored  hole  in  the  pivot 
yoke  enables  that  bearing  to  be  flooded  with  oil. 

Cradle. — The  cradle,  of  cast  steel,  has  a  cylindrical  body  bored 
out  to  receive  the  counter-recoil  spring,  on  the  upper  surface  of 
which  are  guides,  lined  with  bronze,  for  the  recoil  clips  of  the 
gun. 

Two  side  pieces  extending  upward  from  the  cradle  body  have 
trunnions  which  fit  in  the  bronze-lined  trunnion  beds  in  the  pivot 
yoke.  The  outer  ends  of  the  trunnions  are  finished  to  receive  the 
front-sight  brackets. 

Pads  near  the  rear  end  of  the  cradle,  on  either  side,  are  finished 
for  the  rear-sight  brackets  and  shoulder  guards.  The  right  side  of 
the  cradle  at  the  rear  end  has  a  boss  finished  with  a  vertical  hole  to 
receive  the  semi-automatic  breech  mechanism  when  used. 


194  THE  SERVICE  OF  COAST  ARTILLERY 

At  the  bottom  part  of  the  rear  end  of  the  spring  cylinder  is  a 
slotted  lug  to  which  is  attached  the  inner  elevating  screw. 

The  counter-recoil  spring  is  a  single  helical  spring,  with  round 
cross-section,  and  at  assembled  height  it  is  about  12  inches  shorter 
than  at  free  height.  It  is  assembled  from  the  front,  and  the  rear 
end  rests  against  a  flange  on  the  interior  of  the  spring  cylinder  and 
the  forward  end  rests  against  a  flange  on  the  front  recoil-cylinder 
head.  The  counter-recoil  spring  is  coiled  between  the  interior  of 
the  spring  cylinder  and  the  exterior  of  the  recoil  cylinder. 

The  recoil  cylinder  is  of  forged  steel,  finished  all  over,  and 
threaded  at  the  ends  to  receive  the  front  end  rear  recoil-cylinder 
heads.  There  are  flexible  vulcanized  fiber  packings  making  oil- 
tight  the  front  and  rear  ends  of  the  recoil  cylinder.  The  piston  rod 
passes  through  a  stuffing  box  in  the  front  recoil-cylinder  head. 

The  stuffing  box  consists  of  a  finished  bronze  follower  on  the 
piston  rod,  screwed  into  a  box  in  the  front  recoil-cylinder  head,  and 
compressing  five  rings  of  Oarlock's  hydraulic  waterproof  packing 
between  a  flange  in  the  box  and  a  forged-steel  gland,  divided  into 
halves  and  retained  in  position  on  the  follower  by  a  spring-steel 
ring. 

The  front  cylinder  head  is  provided  with  filling  and  drain  holes, 
each  to  be  closed  by  a  bronze  washer-head  filling  and  drain  plug. 

The  spring  cylinder  head  is  of  cast  steel  and  receives  the  piston- 
rod  pull.  It  also  receives  the  thrust  of  the  counter-recoil  spring  at 
assembled  height,  when  the  lug  of  the  gun  is  disconnected  from  the 
rear  cylinder-head  stud,  in  mounting  and  dismounting  the  recoil 
system.  The  instruction  plate  is  mounted  on  the  spring-cylinder 
head. 

The  piston  rod  and  piston  are  in  one  piece,  made  of  forged  steel, 
finished  to  receive  a  bronze  piston  liner  and  bored  out  to  receive  the 
counter-recoil  buffer.  This  buffer  is  made  of  Tobin  bronze,  finished 
so  as  to  be  screwed  into  the  rear  recoil-cylinder  head  from  the  inside. 

There  are  three  throttling  grooves  in  the  interior  of  the  recoil 
cylinder. 

Recoil  and  Counter-Recoil  Systems. — The  action  of  the  carriage 
is  as  follows:  When  fired  the  gun  recoils  to  the  rear  about  9  inches 
in  the  cradle,  carrying  with  it  the  recoil  cylinder  and  thereby  com- 
pressing the  counter-recoil  spring.  A  small  portion  of  the  energy 
of  recoil  is  taken  up  in  compressing  the  counter-recoil  spring,  but 
the  greater  portion  of  the  energy  is  absorbed  by  the  resistance  offered 
by  the  liquid  being  forced  through  the  orifices  of  the  throttling 


ARMAMENT  195 

grooves.  The  width  of  the  grooves  is  uniform,  but  their  depths  are 
proportioned  so  that  the  areas  of  the  orifices  vary  with  the  position 
of  the  piston  during  recoil,  and  will  be  such  as  to  give,  with  the  aid 
of  the  counter-recoil  springs,  a  constant  resistance  throughout  the 
length  of  recoil.  The  pressure  in  the  cylinder  is  therefore  a  uniformly- 
decreasing  one.  The  counter-recoil  buffer  is  tapered  so  that  the 
escape  of  oil  during  counter  recoil  through  the  varying  diametral 
clearances  between  the  buffer  and  the  walls  of  its  hole  will  offer  such 
resistance  as  will  control  the  motion  of  the  gun  during  its  return, 
and  finally  bring  it  to  rest  when  the  recoil  piston  reaches  the  rear 
end  of  the  cylinder. 

Elevating  Mechanism. — The  elevating  mechanism  consists  of  a 
handwheel  actuating  through  suitable  connecting  shafts  and  bevel 
gears,  a  double  screw  with  right-hand  outer  threads  and  left-hand 
inner  threads.  The  outer  elevating  screw  is  of  forged  steel  and  turns 
in  a  bronze  elevating  nut  and  cap.  It  receives  its  rotary  motion 
from  the  elevating  bevel  gear  by  means  of  two  keys  sliding  in  longi- 
tudinal grooves  cut  in  the  outside  of  the  screw.  The  inner  screw 
has  a  left-hand  thread  and  has  its  upper  end  attached  to  the  slotted' 
lug  on  the  bottom  of  the  rear  end  of  the  spring  cylinder.  The 
elevating-screw  nut  is  pivoted  on  trunnions  so  as  to  allow  the 
necessary  rotation,  corresponding  to  different  angles  of  elevation. 
The  elevating-screw  nut  is  provided  with  an  elevating-screw  nut 
cap  bolted  to  it  by  four  bolts.  The  elevating-screw  cap  has  a  hole 
and  plug,  and  the  elevating-screw  nut  has  a  hole  fitted  with  a  plug 
for  draining. 

The  elevating  bevel  gear  is  of  bronze,  and  the  pinion  is  of  forged 
steel.  The  pinion  is  keyed  onto  the  elevating  intermediate  shaft 
which  receives  its  motion  from  the  handwheel  by  the  elevating 
handwheel  shaft  and  a  set  of  elevating  handwheel  shaft  gears  inclosed 
in  gear  covers. 

The  elevating  handwheel  shaft  has  a  bearing  near  the  hand- 
wheel  in  a  bracket  secured  to  the  shoulder  rest.  The  elevating  gear 
bracket  cap  has  a  bearing  for  the  lower  end  of  the  elevating  hand- 
wheel  shaft  and  serves  as  a  cap  for  the  trunnions  of  the  elevating- 
screw  nut. 

Traversing  Mechanism. — The  traversing  mechanism  consists  of  the 
travers  ng  worm  wheel,  traversing  worm  shaft  and  worm,  one  pair 
of  bevel  gears,  one  traversing  shaft,  and  one  traversing  handwheel. 
It  is  all  designed,  however,  so  that  another  handwheel  can  be  placed 
on  the  right-hand  side  if  necessary.  The  traversing  worm  wheel  is 


196  THE  SERVICE  OF  COAST  ARTILLERY 

I 

seated  on  the  exterior  cylindrical  top  of  the  pedestal,  and  is  retained 

in  position  by  the  friction  band,  a  shoulder  on  the  pivot  yoke,  and 
a  shoulder  on  the  pedestal. 

The  friction  band  is  made  in  halves  and  united  by  a  stud  bolt 
screwed  into  a  boss  on  the  front  of  the  pedestal.  By  means  of  a 
bolt  a  certain  amount  of  friction,  between  the  friction  band  and 
the  traversing  worm  wheel,  secures  the  traversing  worm  wheel  to 
the  pedestal  rigidly  enough  to  allow  the  thrust  of  the  traversing 
worm  shaft  to  traverse  the  gun,  but  it  does  not  secure  it  so  rigidly 
that  the  •  teeth  of  the  traversing  worm  wheel  might  be  inj  ured  by 
the  sudden  shock  of  discharge. 

There  is  a  spring  between  the  bolthead  and  the  lug  on  the  friction 
band  so  that  when  the  bolt  is  tightened  enough  to  give  sufficient 
friction  to  enable  the  gun  to  be  traversed  without  slipping,  it  will  yet 
permit  slipping  in  case  undue  strain  is  brought  on  the  teeth  of  the 
worm  wheel.  The  spring  serves  to  regulate  and  keep  uniform,  during 
rotation,  the  pressure  on  the  worm  wheel.  The  traversing  worm 
shaft  is  assembled  with  its  worm  in  the  traversing-gear  case. 

A  pair  of  bevel  gears,  in  a  cast-iron  bevel-gear  cover,  serve  to 
transmit  the  motion  of  the  traversing  handwheel'  and  traversing 
handwheel  shaft,  to  the  left  end  of  the  traversing  worm  shaft.  The 
traversing  handwheel  shaft  is  supported  in  its  proper  position  by 
two  brackets  containing  suitable  bearings.  One  bracket  is  bolted 
to  the  elevating-gear  bracket  and  the  other  is  bolted  to  the  shoulder 
rest. 

Shoulder  Guard. — A  bronze  shoulder  guard,  attached  to  the 
left  side  of  the  cradle  by  four  bolts,  carries  the  firing  mechanism, 
and  protects  the  gunner  on  the  left  side  from  injury  during  recoil 
and  counter  recoil  of  the  gun. 

Shield  and  Supports. — The  shield  consists  of  a  2-inch  nickel-steel 
plate  bent  to  shape,  shielding  the  gun  and  detachment  from  the 
front  only.  It  is  pierced  with  two  ports,  one  for  sighting  and  one 
for  the  gun.  The  shield  is  supported  by  two  shield  supports  bolted 
to  the  pivot  yoke. 

The  center  of  gravity  of  the  shield,  supports,  pivot  yoke,  gun, 
and  charge  is  so  arranged  that  it  falls  through  the  center  of  the  ball- 
thrust  bearing  in  the  pedestal,  thus  limiting  as  much  as  possible  the 
force  necessary  to  elevate  and  traverse  the  gun. 

Shoulder  Rest. — The  carriage  is  provided  with  a  shoulder  rest 
bolted  to  the  pivot  voke  on  the  left  side.  It  is  of  cast  steel,  and  the 
shoulder  end  has  mounted  upon  it  a  2.4-inch  rubber  tube.  The 


ARMAMENT  197 

shoulder  rest  is  finished,  near  its  center,  to  receive  a  bracket  con- 
taining the  traversing  and  elevating  shaft  bearings. 

The  right  side  of  the  pivot  yoke  is  finished  so  that  a  shoulder  rest 
for  the  right-hand  side  may  be  attached,  if  it  is  desired  to  use  two 
sights  and  two  gunners. 

Special  Mounts.— In  addition  to  the  types  of  carriages  described 
above  there  are  some  few  special  types  found  in  the  service.  The 
designs  of  these  carriages,  strictly  speaking,  place  them  under  some 
one  of  the  classes  previously  given,  but  the  details  of  their  construc- 
tion are  such  as  to  make  it  desirable  to  classify  them  separately. 

The  carriages  for  the  4.72-  and  6-inch  Q.-F.  Armstrong  Guns 
(Plates  XI  arid  XV)  are  examples  of  such  carriages  and  a  descrip- 
tion of  the  former  follows: 

The  mounting  consists  of: 

1.  A    cradle    including   hydraulic    recoil    cylinder,    trunnions,    bar 
and  drum  sights,  and  other  parts  and  fittings  complete. 

2.  A  carriage  of  steel  in  the  shape  of  a  Y,  fitted  with  trunnion 
bearings  for  the  cradle,   and  having  a  long  pin,   forming  the  pivot 
of  the  carriage. 

3.  A   circular   shield   with   roof   supported   from   the   carriage   by 
means  of  elastic  stays  or  supports. 

4.  An  elevating  bracket,  fixed  to  the  carriage  carrying  the  elevat- 
ing gear,  shoulder  piece,  and  firing  pistol. 

5.  A  pedestal  or  socket  for  receiving  the  pivot   pin   of  the   car- 
riage. 

Cradle. — The  cradle  is  a  single  casting  of  gun  bronze,  and  com- 
prises the  frame  through  which  the  gun  recoils,  the  hydraulic  recoil 
cylinder,  trunnions,  spring  box,  and  reserve  oil  tank.  The  trunnions 
of  the  cradle  are  supported  by  bearings  machined  in  the  Y-piece, 
the  cradle  moving  with  the  gun  when  it  is  elevated  or  depressed. 
The  hydraulic  recoil  cylinder  is  directly  underneath  the  gun;  it  is 
provided  with  a  piston  and  rod,  forged  in  one  piece.  The  piston 
rod  passes  through  a  gland  at  the  rear  of  the  cylinder,  and  is 
fitted  to  a  projecting  arm  on  the  breech  of  the  gun.  The  cylinder 
is  also  fitted  with  a  valve  key,  controlling  ram,  drain  hole,  and 
air  hole. 

The  action  of  the  carriage  on  firing  is  as  follows:  The  gun  slides 
back  within  the  cradle,  the  force  of  the  recoil  being  transmitted  by 
the  arm  on  the  gun  to  the  piston,  and  the  resistance  offered  by  the 
oil  (with  which  the  cylinder  is  filled)  to  the  motion  of  the  piston 
gradually  overcomes  the  force  of  the  recoil.  The  valve  key  is  of  such 


198  THE  SERVICE  OF  COAST  ARTILLERY 

a  form  as  to  produce,  by  varying  the  size  of  the  opening  in  the  piston 
during  recoil,  an  approximately  uniform  pressure  in  the  recoil  cylinder. 
The  controlling  ram  is  fitted  to  regulate  the  velocity  of  the  gun  when 
returning  to  the  firing  position.  The  spring  box  is  under  the  front 
part  of  the  cradle.  It  contains  two  spiral  springs  for  the  purpose 
of  returning  the  gun  and  retaining  it  in  the  firing  position  after 
recoil.  The  reserve  oil  tank  is  cast  on  the  right  side  of  the  cradle 
and  is  always  in  free  communication  with  the  recoil  cylinder.  Any 
leakage  which  may  occur  from  the  cylinder  is  filled  up  from  the 
tank.  A  suitable  filling  hole  is  provided  at  the  top.  The  cradle  is 
provided  with  bosses  for  the  sights,  and  with  eyes  for  dismounting 
purposes. 

Carriage. — The  carriage  of  Y-piece  carries  the  cradle  and  forms  the 
pivot  upon  which  the  gun  and  mounting  revolve.  The  elastic  stays 
for  shield  and  elevating  and  training-gear  bracket  are  attached  to  the 
sides  of  the  carriage,  an  undercut  groove  being  arranged  for  the  latter 
in  the  casting.  At  the  base  of  the  pivot  pin  is  fitted  a  hardened-steel 
ring,  forming  a  path  for  the  hard  steel  balls,  upon  which  the  Y-piece 
revolves. 

Pedestal. — The  pedestal  consists  of  a  hollow  steel-  casting  in  the 
form  of  a  cone;  the  bottom  of  the  casting  forms  a  socket  for  the  forged- 
steel  pivot  on  the  carriage,  and  is  provided  with  a  bronze  bush  at  the 
lower  end  to  receive  the  foot  of  the  pivot.  A  ball  bearing  consisting  of 
spherical  balls  of  steel  is  fitted  to  take  the  weight  of  the  pivot  and  to 
facilitate  the  training  of  the  mounting. 

Elevating  Gear. — The  elevating  gear  is  carried  by  a  steel  bracket, 
fixed  to  the  left  side  of  the  Y-piece.  It  is  actuated  by  a  handwheel, 
which  is  placed  in  a  convenient  position  to  be  worked  by  the  man 
laying  the  gun.  The  handwheel  drives  by  means  of  a  pair  of  miter 
wheels  a  worm  which  works  the  worm  wheel.  On  the  inner  end  of  the 
shaft  carrying  this  worm  wheel  a  pinion  is  fixed,  which  gears  with  the 
elevating  arc  attached  to  the  carriage. 

The  elevating  gear  is  provided  with  a  frictional  driving  arrangement, 
as  follows :  The  boss  of  the  worm  wheel  is  hollow,  and  contains  a  series 
of  friction  rings,  part  of  which  are  of  steel,  and  are  keyed  to  and  turn 
with  the  shaft,  while  the  remaining  rings  are  of  manganese  bronze, 
and  are  keyed  to  and  turn  with  the  worm  wheel.  These  friction  rings 
are  placed  alternately,  and  are  pressed  together  by  means  of  a  spring- 
steel  washer  and  a  nut  on  the  extreme  end  of  the  shaft.  By  adjusting 
this  nut  the  rings  are  pressed  together  sufficiently  to  produce  the 
requisite  friction  to  prevent  the  gun  running  down  at  extreme  recoil, 


ARMAMENT  199 

but  at  the  same  time  allows  the  gun  to  move  slightly  when  fired  with- 
out giving  motion  to  the  whole  of  the  gear.  The  nut  is  to  be  tightened 
up  if  the  gun  runs  down  when  fired.  An  adjustable  pointer  is  fitted 
so  that  the  amount  of  elevation  may  be  read  off  the  back  of  the  elevating 
arc,  which  is  graduated  for  that  purpose. 

Training  Gear. — The  training  gear  is  fitted  on  the  left  side  of  the 
carriage,  in  a  convenient  position  for  being  worked  by  the  man  at  the 
shoulder  piece.  It  consists  of  a  gun-metal  worm  wheel,  with  a  hollow 
boss,  by  which  it  is  supported  in  the  top  of  the  pedestal,  and  which 
also  forms  a  top  bearing  for  the  pivot  of  the  mounting.  A  worm,  carried 
in  a  gun-metal  bracket  fixed  to  the  carriage,  engages  with  the  worm 
wheel,  the  worm  wheel  is  fixed  to  a  steel  shaft  and  is  worked  by  means 
of  toothed  gear  at  the  rear,  actuated  by  the  handwheel. 

A  gun-metal  friction  block,  which  presses  against  the  boss  of  the 
worm  wheel,  is  fitted  with  a  clamping  screw  in  the  pedestal.  Friction 
between  the  block  and  the  worm  wheel  is  caused  by  the  handle, 
and  is  sufficient  to  enable  the  mounting  to  be  rotated.  By  slackening 
the  clamping  screw  the  mounting  is  free  to  be  trained  by  the  shoulder. 

Shield. — The  mounting  is  fitted  for  its  own  protection,  and  that  of 
the  men  working  the  gun,  with  an  outer  circular  shield  4J  inches  thick, 
and  inner  flat  vertical  shield  3  inches  thick  of  steel  plate.  The  outer 
shield  has  side  wings  2  inches  thick  and  a  flat  roof  1  inch  thick. 

The  shield  is  provided  with  apertures  for  laying  the  gun. 

Instructions  for  Filling  the  Recoil  Cylinder. — Depress  the  gun  and 
take  out  the  filling  and  air  plugs.  Fill  through  the  filling  hole  in  the 
reserve  oil  tank  until  the  oil  outflows  through  the  air  hole;  replace 
the  air  plug,  and  fill  in  until  the  oil  overflows  at  the  filling  hole;  then 
replace  the  filling  plug. 

DISAPPEARING    CARRIAGE 

In  this  type  of  carriage  the  gun  is  raised  above  the  parapet  for 
firing  and  recoils  under  cover  for  loading.  Plates  I,  II,  and  III  show 
in  detail  the  Disappearing  Carriage,  Limited  Fire,  Model  of  1901;  the 
details  of  which  are  as  follows: 

The  Carriage  is  designed  to  mount  guns  of  either  the  model  of 
1895  or  the  model  of  1900.  It  embodies  many  additions  and  improve- 
ments on  the  previous  models,  the  principal  ones  of  which  are  general 
stiffening  of  the  structure,  the  turntable  being  3  inches  deeper;  a  sighting 
platform  along  each  side  of  the  carriage,  accessible  by  ladders  in  front 
and  in  rear;  sight-laying  apparatus,  with  new  3-inch  objective  telescopic 


200  THE  SERVICE  OF  COAST  ARTILLERY 

sight  arranged  to  be  used  by  a  man  on  the  sighting  platform,  who  has 
under  his  own  immediate  control  all  operations  of  laying  and  firing,  if 
desired;  electric  motor  as  well  as  hand  appliances  for  the  operations  of 
traversing,  elevating,  depressing,  and  retracting  the  gun;  the  control  of 
the  electric-motor  equiqment  from  either  the  sighting  or  the  working 
platform;  connections  for  electric  firing  either  by  the  man  at  the  sight 
or  by  the  battery  commander  (in  salvo) ;  the  addition  of  a  safety  appli- 
ance for  electric  firing  and  of  a  safety  lanyard  attachment,  which  prevents 
firing  before  the  gun  is  in  battery;  a  traversing  brake  near  the  auxili- 
ary traversing  controller;  improved  lubricating  appliances,  and  new 
counter-recoil  buffers,  which  permit  of  sufficient  counterweight  being 
used  to  bring  the  gun  into  battery  in  from  five  and  one-half  to  seven 
seconds. 

Stops  can  be  so  arranged  as  to  permit  traversing  either  60,  70,  90, 
or  110  degrees  either  side  of  the  "front"  of  the  battery,  and  the  piece 
can  be  elevated  from  5  degrees  depression  to  10  degrees  elevation, 
stops  being  arranged  to  limit  the  depression  to  either  horizontal  or 
2.5  degrees  depression  when  the  height  of  the  parapet  requires  it. 

When  in  the  execution  of  mechanical  maneuvers  it  may  become 
necessary  to  traverse  the  piece  breech  to  the  front,  which  can  be  done 
with  gun  in  battery;  the  fixed  stops  and  the  cams  of  the  traversing 
controller  stops  must  be  removed  and  care  exercised  that  the  electric 
cable  in  the  pit  is  not  injured  by  traversing  the  counterweight  against  it. 
The  elevating  system  is  so  constructed  that  the  gun  is  at  an  angle  of 
about  4  degrees  elevation  when  in  the  loading  position  if  recoiling  to  the 
thirty-third  notch  with  any  angle  of  elevation  in  battery. 

Action  of  Carriage. — Upon  firing  the  piece  the  gun-lever  axle  is 
moved  to  the  rear  by  the  recoiling  energy  of  the  gun,  carrying  the  top 
carriage  with  it.  The  lower  ends  of  the  levers  move  vertically  upward, 
being  constrained  by  the  crosshead  traveling  on  the  vertical  crosshead 
guides.  The  trunnions  of  the  gun  move  downward  and  to  the  rear. 
The  energy  of  recoil  is  absorbed  partly  by  raising  the  counterweight  and 
partly  by  the  movement  of  the  masses  up  the  inclined  chassis  rails,  but 
principally  by  the  resistance  of  the  recoil  cylinders;  and  when  the  gun 
comes  to  rest  it  has  the  proper  loading  angle.  After  loading,  the  pawls 
are  tripped,  and  the  excess  of  the  moment  of  the  counterweight  over  the 
moment  of  the  gun,  enables  it  to  raise  the  gun  to  the  firing  position. 
If  this  excess  be  small,  the  velocity  of  counter  recoil  will  be  slow;  but 
if  more  counterweight  be  added,  the  velocity  will  increase  and  the  time 
required  for  going  into  battery  decrease. 

Principal    Parts. — The  carriage  consists  of  the  following  principal 


ARMAMENT  201 

parts,  viz.:  Base  ring,  azimuth  circle  and  pointer,  traversing  roller 
system,  racer,  clips  and  dust  guards,  chassis  and  transoms,  top  carriage 
and  recoil  rollers,  recoil  and  counter-recoil  system,  gun  levers,  crosshead, 
tripping  gear,  counterweight,  elevating  arm,  band  and  slide,  elevation 
and  range  scales  and  pointers;  elevating,  traversing,  and  retracting 
systems;  working  platform,  sighting  standards  and  platforms,  sight 
standard  and  laying  mechanism,  safety  lanyard  attachment;  electric 
safety  firing  attachments;  electric  motor  equipment  for  traversing, 
elevating  and  depressing,  and  retracting  the  gun,  conduits,  wiring, 
and  illumination;  accessories,  including  ammunition  trucks,  shot  tongs, 
and  implements. 

Base  Ring. — The  base  ring,  19  feet  in  diameter,  is  made  of  cast  iron, 
in  halves,  bolted  and  keyed  together,  and  is  held  in  position  on  the 
foundation  by  twelve  2.75-inch  bolts.  Twelve  screws  for  leveling  the 
base  ring  are  set  against  steel  plates  through  which  the  foundation  bolts 
pass. 

The  base  ring,  in  addition  to  having  the  lower  roller  path  on  its  upper 
surface,  has  an  annular  flange  near  its  inner  edge  forming  the  pintle  for 
the  carriage.  This  flange  has  near  its  top  edge  a  lip  inward  under  which 
the  clips  engage,  and  on  its  top  edge  the  azimuth  circle.  The  inner  edge 
of  the  lip  is  rabbeted  to  receive  the  felt  and  steel  inner  dust-guard  strips. 
The  outer  annular  flange  on  the  ring  projects  downward  into  the  plat- 
form and  upward  outside  of  the  traversing  rollers.  The  cavities  on  each 
side  of  the  roller  path  are  drained  into  the  pit  through  passages  closed 
by  screw  plugs  in  the  inner  edge  of  the  ring. 

Tapped  holes  can  be  found  inside  of  the  pintle  flange  for  attaching 
the  traversing  stops  in  any  required  position. 

The  base  ring  is  marked  "front"  and  "rear"  in  raised  letters  cast 
on  the  top  surface  between  bolt  holes. 

Azimuth  Circle  and  Pointer. — A  brass  azimuth  circle,  attached 
by  countersunk  screws  to  the  top  of  the  pintle  of  the  base  ring,  is 
graduated  in  degrees,  the  numbers  of  which  are  to  be  added  after  the 
carriage  is  erected  in  its  emplacement.  The  top  of  the  racer  is  cut 
away  on  the  left  side  to  expose  the  azimuth  circle  and  the  micrometer 
pointer  and  the  subscale,  fastened  to  the  racer.  The  subscale  has 
slotted  holes  to  give  it  a  lateral  motion  for  adjustment,  after  which  it 
is  fixed  in  position  by  two  dowels.  It  is  graduated  and  stamped  in 
decimals  of  a  degree,  the  least  reading  being  0.1  of  a  degree.  The 
micrometer  screw,  actuating  the  pointer,  is  graduated  to  a  least  read- 
ing of  0.01  of  a  degree.  The  subscale  and  pointer  is  protected  by  a 
hinged  bronze  cover. 


202  THE  SERVICE  OF  COAST  ARTILLERY 

Traversing  Roller  System. — The  racer  rests  and  is  traversed  upon 
a  circle  of  twenty-four  live,  conical,  traversing  rollers,  whose  axes  are 
maintained  in  the  radial  position  by  bearings  bolted  to  distance  rings. 
They  are  of  forged  steel,  solid,  with  a  journal  beyond  each  end  and 
with  flanges  on  their  inner,  small  ends. 

The  distance  rings  are  cast  together,  of  steel,  and  made  up  in  six 
sections,  bolted  together,  and  have  bolted  on  their  upper  surfaces  the 
bronze  bearings  for  the  traversing  rollers.  The  bearings  are  formed 
with  a  loop  on  top  by  means  of  which  any  roller  with  its  bearings  can 
be  lifted  out  of  the  ring  through  the  holes  at  the  racer  joints. 

The  system  is  kept  concentric  with  the  pintle  by  the  flanges  on  the 
rollers  in  centrifugal  contact  with  the  inner  edge  of  the  roller  path  on 
the  base  ring.  The  inner  edge  of  the  path  on  the  racer  is  of  a  larger 
diameter  so  as  not  to  come  in  contact  with  the  flanges. 

Racer. — The  racer  is  made  of  steel,  17  feet  and  10  inches  in  diameter, 
cast  in  halves,  bolted  and  keyed  together  with  the  joints  on  the  side 
of  the  carriage.  On  each  side  of  the  joints  are  two  openings,  with 
removable  cover  plates,  through  which  four  recoil  rollers  may  be  lifted 
out  at  a  time  for  cleaning. 

It  is  of  box  section,  and,  in  addition  to  having  the  upper  roller  path 
on  its  under  surface,  has  an  annular  flange  lined  with  bronze  near  its 
inner  edge  and  fitting  over  the  pintle,  with  0.04-inch  diametral  clearance. 

Upon  its  top  surface  the  chassis  and  transom  are  bolted,  doweled, 
and  keyed,  and  on  its  outer  wall  the  working  platform  and  traversing- 
controller  stop  brackets  are  bolted  to  pads. 

Two  oil  holes  on  each  side  near  the  chassis  with  connecting  grooves 
provide  means  for  oiling  the  pintle. 

The  traversing-roller  journals  are  oiled  by  removing  four  oil  plugs 
on  each  side  near  the  racer.  In  this  case  the  oil  drops  into  annular 
grooves  on  top  of  the  distance  rings  and  must  be  supplied  between 
each  roller,  thus  requiring  traversing  90  degrees. 

Two  additional  oil  holes,  placed  30  degrees  on  each  side  of  each  joint 
and  closed  with  0.75  bronze  countersunk  screws,  are  for  occasional  use. 

Clips  and  Dust  Guards. — Two  clips  in  front  and  one  in  rear  are 
bolted  down  on  top  of  the  inner  edge  of  the  racer  and  engage  under 
the  lip  inside  of  the  pintle  flange.  The  rear  clip  extends  still  lower  in 
the  form  of  a  lug,  which  strikes  the  stops,  limiting  the  traversing 
movement. 

A  dust  guard,  of  angle  iron,  in  six  sections,  with  handles,  is  bolted 
to  the  top  edge  of  the  outer  flange  on  base  ring. 

Felt,  and  steel  pinching  strips,  inclosing  the  roller  system  dust  tight, 


ARMAMENT  203 

are  bolted  to  the  top  edge  of  the  dust  guard  outside  and  the  pintle 
flange  inside  of  the  roller  paths,  the  felt  being  compressed  against  the 
opposite  racer  surfaces.  The  dust-guard  sections,  with  their  felt  strips, 
are  easily  removed. 

Chassis  and  Transoms. — The  chassis  of  cast  iron  is  bolted,  doweled, 
and  keyed  to  the  racer  and  are  united  at  their  front  and  rear  ends  by 
cast-steel  transoms,  also  bolted  to  the  racer.  The  rear  transom  carries 
the  elevating  slide  and  gearing.  The  upper  surfaces  of  the  chassis 
form  the  recoil-roller  path  and  slope  1  degree  and  20  minutes  to  the 
front  to  facilitate  the  return  of  the  piece  to  the  firing  position,  thus 
reducing  the  necessary  preponderance  of  the  counterweight. 

The  chassis  also  provide  the  necessary  bearings  or  supports  for  all 
the  mechanism  and,  with  the  racer,  supports  for  all  the  minor  attach- 
ments. 

The  crosshead  guides  are  machined  flush  on  the  inside  and  near  the 
front  end.  They  extend  from  below  the  racer  to  above  the  top  of  the 
piston-rod  lugs. 

Stops  are  machined  in  rear  of  the  lugs  against  which  the  top  carriage 
and  recoil  rollers  come  to  a  rest  when  entirely  in  battery. 

Top  Carriage  and  Recoil  Rollers. — The  top  carriage,  which  is 
similar  to  that  of  an  ordinary  barbette  carriage,  is  made  of  steel,  cast 
in  one  piece.  It  consists  of  two  side  frames  containing  the  beds  for  the 
gun-lever  axles,  and  two  recoil  cylinders,  all  united  by  transoms.  It  rests 
upon  two  sets  of  13  live  recoil  rollers  which  are  bushed  with  bronze 
and  run  on  steel  axles  set  into  movable  steel  cages.  The  rollers  are  of 
forged  steel  and  flanged  on  both  ends  to  guide  the  top  carriage  upon  the 
chassis.  They  move  to  the  rear  with  the  top  carriage  at  half  its  speed 
and  travel  half  as  far. 

Lugs  project  from  the  lower  front  part  of  the  top  carriage,  which 
serve  as  fulcra  for  pinch  bars  held  horizontally  and  engaging  with  teeth 
cast  on  the  chassis  rail,  by  which  arrangement  the  top  carriage  may  be 
moved  forward  to  the  firing  position  against  the  stop  if  for  any  cause  it 
should  fail  to  come  fully  into  battery.  When  time  permits,  the  top 
carriage  should  always  be  brought  fully  into  battery  (against  the  stops) ; 
but,  if  desired,  the  gun  may  be  fired  when  the  top  carriage  is  as  much  as 
3  inches  out  of  battery  with  perfect  safety  and  with  no  bad  results  other 
than  inaccuracy  in  the  elevation  of  the  gun,  unless  this  elevation  be 
given  by  telescopic  sight  on  gun  trunnion,  or  by  quadrant  on  the 
gun. 

Clips  projecting  from  the  lower  rear  part  of  the  top  carriage  engage 
under  flanges  on  the  top  of  the  chassis  to  prevent  the  carriage  from 


204 


THE  SERVICE  OF  COAST  ARTILLERY 


tipping  forward  upon  striking  the  stops  in  returning  to  the  firing 
position. 

The  axle  beds  in  the  side  frames  are  provided  with  caps  clipped  on 
and  secured  from  lifting  off  by  four  studs  each,  having  nuts  and  check 
nuts.  The  caps  and  beds  are  lined  with  bronze  half  bushings. 

Recoil  and  Counter-recoil  System. — Figure  18  shows  the  general 
arrangement  of  the  hydraulic  brake  and  its  connections  in  its 
essential  principles  and  in  relative  positions  of  parts  for  disappearing 
carriages  "in  battery." 

The  recoil  cylinders  are  lined  with  cast  iron  and  are  13  inches  in 
interior  diameter,  with  piston  rods  4.75  inches  in  diameter,  having 
pistons  and  counter-recoil  buffer  plungers  forged  solid  with  them.  The 


gecliort.  fr-fr  shstxrisiff  maximum 
^  tsfan  SeecuZ of  t/te 


Coast -fer  Jfecei£ 


o/ienintrs  tstnision 
juuxd  closed  a*  &te 
esu*  of  Met  recoeC. 


Stecoil J 


I , 


Jtecotz 


I 


GENERAL  METHOD  OF  CONTROLLING  THE  ENERGY 
OF  RECOIL  IN  GUN  CARRIAGES. 

FIG.  18. 


rods  are  secured  by  nuts  and  check  nuts  to  upright  lugs  on  the  chassis, 
and  extending  through  the  rear  cylinder  heads,  their  rear  ends  are 
supported  by  brackets  bolted  to  the  chassis.  At  the  ends  of  the 
cylinders  there  are  the  usual  stuffing  boxes  with  glands  and  followers. 
The  counter-recoil  buffers  are  formed  by  annular  projections  cast 
on  the  rear  cylinder  heads,  which  fit  into  the  cylinder  and  are  supported 
by  its  walls,  and  which  are  bushed  with  bronze  inside.  In  the  recesses 
thus  formed  fit  tapering  plungers  on  the  piston  rods.  When  the  gun 
returns  to  the  firing  position  the  liquid  caught  in  the  recesses  in  the 
cylinder  heads  can  escape  only  through  the  small  clearance  between 
the  plunger  and  the  walls  of  the  recess,  thus  acting  as  a  hydraulic 
buffer  or  dashpot  to  check  the  velocity  at  the  end  of  the  return  "  into 


ARMAMENT  205 

battery."  At  the  front  end  of  the  chassis  rails  counter-recoil  stops 
are  provided  to  prevent  the  bottoming  of  the  buffer  plungers  in  the 
annular  recesses.  Against  these  stops  the  top  carriage  abuts  when  in 
the  firing  position. 

Each  cylinder  has  one  filling  hole  near  its  front  lower  end. 

That  portion  of  the  cylinder  above  the  level  of  the  filling  holes 
(about  750  cubic  inches  in  each  cylinder)  is  intended  to  be  empty,  this 
being  for  the  purpose  of  allowing  the  oil  sufficient  space  in  which  to 
expand  when  heated  by  weather  or  the  friction  developed  in  firing, 
and  to  provide  a  space  into  which  the  plunger  of  the  counter-recoil 
buffer  may  be  withdrawn.  This  withdrawal  is  accomplished  so  rapidly 
in  recoil  that  the  oil  cannot  flow  through  the  small  clearances  and  fill 
the  seat  of  the  buffer  without  the  development  of  a  very  high  .pressure 
in  the  cylinder,  which  would  be  undesirable. 

To  secure  equal  resistance  and  equal  fluid  pressure  in  the  two  cylin- 
ders an  equalizing  pipe  connects  their  front  or  pressure  ends.  In  this 
pipe  is  an  emptying  coupling  by  which  the  whole  recoil  system  can  be 
emptied  of  oil.  From  this  coupling  a  connecting  pipe  extends  back 
tc  the  throttling  valve,  and  from  this  valve  pipes  connect  with  the  rear 
ends  of  the  cylinders. 

Bronze  plugs  are  provided,  to  be  screwed  into  the  cylinders  in  place 
of  the  equalizing  and  throttling  pipes,  thus  continuing  the  piece  in 
action  should  the  pipes  be  destroyed. 

During  the  recoil  the  pistons  remain  stationary  and  the  top  carriage 
with  its  cylinders  is  drawn  over  them.  Each  piston  is  slotted  through 
its  opposite  sides  and  two  throttling  bars  lie  in  the  slots  and  are  bolted 
the  whole  length  of  each  cylinder.  Their  sectional  area  is  such  that 
the  orifices  for  the  flow  of  the  liquid  vary  with  the  position  of  the  piston 
during  recoil  so  as  to  attain  the  desired  resistance  in  the  cylinders. 

In  any  hydraulic  brake  the  resistance  is  greater  as  the  velocity  of 
the  piston  in  the  cylinder  is  greater  and  as  the  openings  for  the  passage 
of  the  liquid  are  less.  The  velocity  of  retarded  recoil  of  the  top  car- 
riage being  variable  and  a  constant  resistance  being  desired,  the  orifices 
are  usually  varied  in  such  manner  that  the  relation  between  the  velocity 
and  the  area  of  the  orifices  is  at  all  points  such  as  to  give  a  nearly  con- 
stant resistance. 

Uniform  resistance  to  the  motion  of  the  top  carriage  is  obtained,  its 
motion  retarded  and  finally  stopped  and  the  energy  of  recoil  taken  up, 
principally  by  the  resistance  which  the  oil  in  the  cylinders  offers  to 
being  forced  from  one  side  of  the  piston  to  the  other,  through  the  fol- 
lowing openings: 


206  THE  SERVICE  OF  COAST  ARTILLERY 

1.  The  clearance  between  the  walls  of  the  cylinder  and  the  piston, 
necessary  for  working  movement.     This  opening  is  of  constant  area. 

2.  The  orifices  between  the  throttling  bars  and  their  slots  in  the 
piston.     These  openings  vary  with  the  profile  of  the  throttling  bars, 
since  the  slots,  which  are  partly  closed  by  these  bars,  are  of  constant 
area. 

3.  The  opening  of  the  throttling  valve  which  controls  the  flow 
through  the  pipes  connecting  the  front  and  rear  ends  of  the  cylinders. 
This  opening  is  of  constant  area  during  recoil,  but  can  be  completely 
closed  or  changed  to  suit  different  conditions  of  loading  and  to  correct 
for  any  other  conditions  that  would  cause  a  variation  in  the  length  of 
recoil. 

The  two  throttling  bars  in  each  cylinder  are  constructed  of  constant 
width  having  only  a  sufficient  lateral  clearance  in  the  slots  for  working 
movement,  and  of  varying  depth,  the  profile  being  so  designed  that  the 
area  of  the  orifices  (the  portions  of  the  slots  not  filled  by  the  bars)  for  the 
escape  of  the  oil  past  the  piston  increases  from  beginning  of  motion  up 
to  the  point  where  the  velocity  of  retarded  recoil  of  the  top  carriage 
is  greatest;  beyond  this  point  the  velocity  of  retarded  recoil  of  the  top 
carriage  is  continually  decreasing  and  the  area  of  the  orifice  decreases 
also  until  it  becomes  zero  at  the  end  of  recoil.  The  orifices  have  at 
each  point  of  recoil  such  a  relation  to  the  velocity  of  retarded  recoil  of 
the  top  carriage  at  that  point  as  to  give  merely  a  constant  resistance  to 
the  motion  of  the  top  carriage.  This  results  in  a  merely  constant  fluid 
pressure  in  the  cylinders. 

The  areas  of  the  orifices  have  to  be  calculated  for  a  particular  set 
of  conditions  of  loading,  and  any  variation  in  these  conditions  will 
change  the  length  of  recoil  of  the  top  carriage,  and  consequently  the 
height  and  inclination  of  the  breech  of  the  gun  in  the  recoil  position. 
As  the  standard  conditions  of  loading  do  not  always  exist,  it  has  been 
found  desirable  to  provide  means  for  varying  the  resistance  of  the 
hydraulic  recoil  brake  in  order  that  the  prescribed  length  of  recoil 
(bringing  the  gun  into  the  prescribed  loading  position)  may  be  obtained 
under  any  conditions,  standard  or  not  standard — as,  for  example,  when 
charges  other  than  full  service  are  fired. 

For  this  purpose  the  equalizing  pipes  between  the  front  ends  of  tho 
cylinders  are  connected  with  the  throttling  pipes  between  their  rear 
ends  through  the  emptying  coupling  and  a  throttling  valve,  providing 
oil  passages  from  the  front  or  pressure  to  the  rear  side  of  the  pistons, 
which  can  be  completely  closed  or  changed  in  area.  (This  throttling 
valve  can  be  adjusted  to  give  openings  varying  by  0.025  square  inch  from 


ARMAMENT  207 

zero  to  0.55  square  inch.}  The  graduations  of  the  valve  are  stamped  on  the 
top  of  the  body,  there  being  11  divisions,  numbered  0,  0.05,  0.10,  etc. 
(One  complete  turn  of  the  valve  effects  the  change  of  0.05  square  inch  in 
the  opening.  One-half  turn  effects  a  change  0.025  square  inch.)  One 
complete  turn  of  the  valve  yoke  generally  changes  the  length  of  recoil  by 
the  equivalent  of  3  or  4  notches  on  the  crosshead  rack.  This  is  liable 
to  vary  by  a  notch  or  more  for  different  carriages  or  for  the  same  car- 
riage under  different  conditions. 

The  setting  of  the  valve  best  suited  to  different  conditions  of  loading, 
full  or  practice  charges,  etc.,  can  be  determined  only  by  experience  in  actual 
firings  with  each  particular  carriage.  For  carriages  on  which  new  buffer 
valves  have  been  attached  see  how  to  set  valves  as  described  under 
"  BUFFER  VALVE."  Different  carriages  may  require  different  settings, 
and  the  same  carriage  may  even  at  different  times  require  different  set- 
tings for  the  same  conditions  of  loading  if  it  is  in  a  materially  different 
condition  as  to  cleanness  and  lubrication  of  the  working  parts,  etc.  It 
is  necessary,  therefore,  that  careful  records  be  kept,  not  only  of  the 
setting  of  the  valve,  the  conditions  of  loading  and  recoil,  but  also  of 
the  elevation  of  the  piece  and  any  abnormal  condition  of  the  carriage 
which  might  affect  the  freedom  of  its  operation.  These  records  should 
be  studied  in  the  light  of  all  these  circumstances  to  obtain  perfect  work- 
ing. However,  the  ammunition  trucks  are  so  designed  that  the  loading 
position  may  vary  somewhat  without  material  inconvenience,  and  it  is 
generally  possible  after  a  few  firings  with  a  carriage  to  determine  the 
setting  of  the  valve  which  will  result  in  the  gun  coming  into  a  proper 
loading  position  for  any  conditions  of  loading.  For  full  charges  the 
valve  should,  in  the  lack  of  experience  with  the  particular  carriage,  be  opened 
to  about  0.15  square  inch,  but  not  more. 

A  padlock  is  provided  for  locking  the  valve  yoke  in  any  position 
to  guard  against  accidental  or  unauthorized  changes  in  the  position  of 
the  valve  after  it  has  been  set.  The  valve  should  habitually  be  kept 
locked,  but  this  should  not  be  understood  as  discouraging  examination 
and  manipulation  of  the  valve,  which  are,  on  the  contrarj^  highly 
desirable  for  the  sake  of  familiarizing  the  personnel  with  its  construc- 
tion and  operation. 

For  all  charges,  the  cylinders  should  be  filled  to  the  level  of  the  filling 
holes,  removing  for  this  purpose  both  plugs  so  as  to  permit  the  air  to 
escape. 

A  neutral  oil,  of  specific  gravity  about  0.85  (such  as  the  "hydro- 
line"  at  present  issued),  is  used,  and  with  this  oil  the  working  pres- 
sure in  the  cylinders  is  about  1,200  pounds  per  square  inch.  A  denser 


208  THE  SERVICE  OF  COAST  ARTILLERY 

oil  would  cause  a  higher  pressure  in  the  cylinders  and  therefore  shorten 
the  recoil  slightly. 

For  the  purpose  of  reducing  the  shock  of  accidental  excessive  recoil, 
recoil  buffers,  made  up  of  alternate  layers  of  balata  and  steel  plates, 
are  placed  on  brackets  bolted  to  the  rear  of  the  chassis,  where  they 
will  be  struck  by  the  upper  ends  of  the  gun  levers  if  the  gun  is  re- 
tracted or  recoils  beyond  its  proper  position. 

The  notches  between  the  ratchet  teeth  cut  on  the  front  faces  of 
the  crosshead  clips  are  numbered  from  the  top,  the  numbers  being 
opposite  the  notches  on  brass  strips  screwed  to  the  crosshead.  When 
the  top  pawl  teeth,  indicated  by  brass  arrows  screwed  to  the  pawl 
levers,  engage  in  the  thirty-third  notch  the  gun  is  in  its  calculated 
loading  position,  below  which  it  'should  not  be  retracted.  By  a  proper 
adjustment  of  the  throttling  valve  the  recoil  of  the  gun  should  not 
vary  much  from  this  position.  The  ammunition  truck  will,  however, 
permit  the  gun  to  be  loaded  anywhere  between  its  position  when  the 
pawls  engage  in  the  twentieth  notch  and  the  lowest  possible  position- 
gun  levers  on  the  balata  counter-recoil  buffers. 

In  case  the  gun  recoils  far  enough  for  the  pawls  to  engage,  but  not 
sufficiently  for  loading,  it  may  be  brought  down  by  the  use  of  the 
retracting  gear. 

From  the  foregoing  description  of  the  recoil  system  it  should  be 
evident  that  should  the  carriage  recoil  too  freely  the  proper  correction 
is  in  a  diminution  of  the  opening  of  the  throttling  valve,  not  in  an 
increase  of  the  counterweight.  On  the  other  hand,  the  counterweight 
alone  should  be  changed  to  correct  or  modify  the  counter-recoil. 

The  amount  of  counterweight  can  be  determined  by  trial.  However 
much  of  the  counterweight  furnished  be  used,  it  will  not  materially 
affect  the  length  of  recoil. 

On  account  of  the  efficient  counter-recoil  buffers,  considerably  more 
counterweight  (5,000  or  6,000  pounds  or  more)  can  be  employed  on 
this  carriage  than  is  necessary  to  bring  the  gun  to  the  firing  position, 
without  injury  to  the  buffer  or  cylinders  or  injurious  shock  to  any  part 
of  the  carriage.  This  extra  counterweight  acts  to  accelerate  the  counter- 
recoil  and  thus  the  time  of  going  into  battery  completely  is  reduced  to 
5^  to  7  seconds  from  the  instant  of  tripping. 

Gun  Levers. — The  two  levers  are  made  of  cast  steel  connected 
near  their  upper  ends  by  a  cast-steel  yoke  firmly  bolted,  and  at  a  point 
a  little  below  their  middle  by  the  forged-steel  gun-lever  axle,  which  is 
fastened  to  the  lever  by  bolts  passing  through  its  heavy  flanges.  The 
gun  levers  are  supported  by  this  axle,  the  projecting  ends  of  which 


ARMAMENT  209 

serve  as  trunnions  supported  by  and  rotating  in  the  axle  beds  in  the 
top  carriage. 

The  upper  arms  of  the  levers  support  the  gun  and  from  their  lower 
ends  the  counterweight  is  suspended  by  crosshead  pins. 

The  trunnion  beds  are  provided  with  cap  squares  clipped  on  and 
secured  from  lifting  off  by  two  studs  each,  having  nuts  and  check 
nuts.  The  caps  and  beds  are  lined  with  bronze  half  bushings. 

Crosshead. — The  crosshead,  of  cast  steel,  is  connected  by  pins  to 
the  gun  levers  and  from  it  the  counterweight  is  suspended  by  four 
keyed  rods. 

Clips  formed  in  one  piece  with  the  crosshead  are  lined  with  bronze 
and  engage  over  crosshead  guides  cast  on  the  inside  of  the  chassis 
rails.  These  guides  constrain  the  crosshead  to  move  in  a  vertical 
direction. 

Ratchet  teeth  are  cut  on  the  front  faces  of  the  clips,  to  be  caught 
by  pawls  pivoted  to  the  chassis  rails,  and  in  this  way  the  counter- 
weight is  held  up  and  the  gun  is  prevented  from  returning  to  the  firing- 
position  after  recoiling. 

Tripping  Gear. — After  the  gun  is  loaded  it  is  permitted  to  rise  to 
the  firing  position  by  raising  the  tripping  levers  until  they  unlatch, 
and  immediately  leaving  them  in  that  position. 

The  action  is  entirely  automatic  after  the  pawls  are  latched  out  of 
engagement  and  the  gun  starts  into  battery.  After  the  crosshead 
teeth  have  passed  entirely  below  the  pawl  teeth  and  the  gun  is  nearly 
in  battery  the  pawl  levers  are  released  from  the  latches  by  the  auto- 
matic action  of  dogs  on  the  crosshead,  and  are  returned  by  the  moment 
of  the  weight  of  the  tripping  levers,  to  their  proper  positions  ready  to 
engage  the  crosshead  when  it  again  rises.  The  pawls  may  be  tripped 
by  the  use  of  one  or  both  levers.  The  levers  should  not  be  raised 
while  the  gun  is  in  battery,  but  should  the  pawls  become  latched  out 
of  engagement  at  this  time,  the  rising  of  the  crosshead  will  again  release 
them  for  engagement. 

Counterweight,  Bottom  Plates,  and  Suspension  Rods. — The 
bottom  plate,  of  cast  steel,  and  the  four  rods  which  suspend  it  from 
the  crosshead  form  the  cage  which  carries  the  lead  counterweight. 
The  counterweight  is  piled  in  the  cage  in  layers  of  different  thicknesses, 
each  layer  consisting  of  two  or  more  pieces.  There  are  72  smaller 
pieces  on  top  provided  with  rings  for  easy  handling.  These  weigh  in 
all  about  5,967  pounds.  By  adding  or  removing  some  or  all  of  these 
smaller  weights  the  counterweight  can  be  readily  increased  or  dimin- 
ished. The  total  amount  of  lead  counterweight  furnished  with  the 


210  THE  SERVICE  OF  COAST  ARTILLERY 

model  of  1895  rifle  is  98  pieces,  weighing  approximately  142,011 
pounds,  and  forming  a  pile,  including  bottom  of  cage,  7  feet  10.25 
inches  high.  That  furnished  with  the  model  of  1900  rifle  is  102  pieces, 
weighing  approximately  164,705  pounds,  and  forming  a  pile  9  feet 
high.  In  some  carriages  there  is  an  extra  layer  3.6  inches  thick,  the 
first  nine  layers  being  6.35  inches  instead  of  6.75  inches  thick.  The 
total  height  and  weight  are  the  same. 

The  amount  of  lead  counterweight  sent  with  each  carriage  is 
designed  to  be  5,000  or  6,000  pounds  in  excess  of  that  required  to 
raise  the  gun  to  the  firing  position  under  normal  conditions.  No  mat- 
ter what  charge  be  used,  the  counterweight  used  should  be  such  as  will 
raise  the  gun  completely  to  the  firing  position  in  about  five  and  one- 
half  to  seven  seconds,  but  should  never  be  such  as  to  cause  the  top 
carriage  to  strike  the  counter-recoil  stops  with  great  shock.  In  its 
lowest  position  the  counterweight  hangs  in  a  well  formed  in  the  con- 
crete platform  concentric  with  the  base  ring  12  feet  6  inches  in  diame- 
ter and  not  less  than  93  inches  in  depth,  measured  from  the  under  side 
of  the  base  ring.  Access  to  the  bottom  of  the  pit  is  obtained  by  means 
of  a  ladder  and  a  manhole  in  the  right  inside  platform. 

Elevating  Arm,  Band,  and  Slide. — The  elevating  arm  of  cast 
steel  carries  a  fixed  double-ended  pin  at  its  lower  end,  rotating  in 
bearings  in  the  elevating  slide,  and  has  two  solid  bronze-bushed  bear- 
ings at  its  upper  end  for  the  elevating-band  trunnions. 

The  band  is  of  cast  steel,  with  inserted  trunnions  screwed  to  their 
conical  seats  and  with  teats  on  their  inner  end,  which  enter  shallow  holes 
in  the  gun  at  accurate  distance  from  the  trunnions  on  each  side  and  in 
the  same  horizontal  plane  with  them.  The  band  is  tightly  clamped 
around  the  gun  by  two  heavy  bolts.  Their  inside  diameters  are  for 
the  gun  of  the  model  of  1900,  48.5  inches,  and  that  for  model  of  1895 
44.5  inches. 

The  elevating  slide  is  moved  by  the  elevating-gearing  system,  in  an 
inclined  guideway  machined  on  the  rear  face  of  the  rear  transom,  which 
guideway  allows  it  the  movement  necessary  to  change  the  elevation  of 
the  gun  from  5  degrees  depression  to  10  degrees  elevation.  There  is 
provided  a  removable  stop,  to  be  placed  in  holes  in  the  right  side  of 
the  guideway  and  above  the  slide,  limiting  the  depression  to  either  0 
or  2.5  degrees,  as  may  be  required  by  the  parapet  over  which  the  gun 
is  to  be  fired. 

While  theory  requires,  in  order  that  the  gun  when  recoiled  to  the 
thirty-third  notch  shall  always  return  to  the  same  angle  for  loading, 
with  the  breech  at  the  same  height,  whatever  may  be  the  firing  angle, 


ARMAMENT  211 

that  the  elevating  slide  and  its  guideway  shall  be  circular  and  struck 
with  radii,  using  the  center  of  the  trunnion  on  the  elevating  band, 
when  the  gun  is  in  the  loading  position,  as  a  center,  yet  the  expenses 
of  manufacture  have  made  it  desirable  to  make  the  slide  and  guideway 
straight.  These  are  so  placed,  however,  as  to  cause  only  a  slight  varia- 
tion in  the  height  of  the  breech  and  in  the  loading  angle. 

Range  and  Elevation  Scale  and  Pointer. — To  the  elevating  slide 
is  bolted  a  bronze  elevating  scale  carrying  straight  German  silver 
scales,  graduated  in  degrees  and  minutes  of  elevation  and  in  yards  of 
range. 

On  account  of  the  character  of  the  motion  of  the  parts  the  distances 
between  the  successive  degree  marks  on  the  elevation  scale  are  not  the 
same,  requiring  the  scale  to  be  graduated  by  the  use  of  a  clinometer 
supported  by  a  rest  placed  in  the  muzzle  of  the  gun,  after  the  gun  is 
mounted  upon  the  carriage,  at  the  time  of  the  shop  test. 

As  the  ranges  corresponding  to  different  angles  of  elevation  above 
the  horizontal  depend  upon  the  height  at  which  the  gun  is  mounted 
above  the  sea  level,  the  range  scale  must  be  graduated  after  mounting, 
the  ranges  corresponding  to  the  different  angles  of  elevation  for  the 
height  above  sea  level,  and  for  the  muzzle  velocity  normally  used  must 
be  calculated  from  the  range  tables  and  formulas  and  marked  upon  the 
scale  in  the  proper  place.  This  should  never  be  done  except  under  the 
supervision  of  the  Ordnance  Department. 

In  smooth  contact  with  the  scale  and  attached  to  the  rear  transom 
by  bolts  in  oblong  bolt  holes  is  a  range  and  elevation  pointer,  having, 
on  account  of  the  oblong  bolt  holes,  a  motion  to  permit  any  needed 
adjustments,  after  which  it  is  to  be  fixed  in  position  by  two  dowels. 

There  has  been  attached  for  trial  upon  the  first  carriage  of  this 
model  a  circular  elevation  and  range  scale  which,  if  found  satisfactory, 
will  be  substituted  for  this  straight  scale  upon  succeeding  carriages. 
The  advantages  of  such  a  scale  are  that  it  can  be  placed  outside  of  the 
chassis,  where  it  is  more  convenient  for  reading,  and  that  it  can  be  made 
of  greater  length  with  corresponding  increase  of  the  size  of  the  smallest 
sub-division.  It  consists  of  a  circular  wheel  carrying  the  graduated 
scale  at  its  outer  circumference  and  mounted  upon  a  shaft  which  has 
keyed  to  its  inner  end  a  pinion  engaging  in  a  rack  bolted  to  the  ele- 
vating slide  in  the  place  of  the  straight  scale.  The  up  and  down 
motion  of  this  rack  rotates  the  pinion  and  shaft  and  the  circular  wheel 
carrying  the  scale.  The  pointer  is  similar  to  that  for  the  straight 
scale  except  it  is  curved. 

It  is  probable  that  the  range  scale  will  be  improved  by  making 


212  THE  SERVICE  OF  COAST  ARTILLERY 

each  range  graduation  correct  for  all  muzzle  velocities  from  the  minimum 
now  in  use  to  the  maximum  probably  obtainable  in  the  future.  These 
graduation  lines  will  of  necessity  be  curved  so  that  one  end  will  be 
correct  for  the  minimum  velocity,  the  opposite  end  for  the  maximum 
velocity,  and  intermediate  points  for  intermediate  velocities.  A  sliding 
index  or  pointer  will  be  used  to  indicate  the  correct  elevations  for 
corresponding  velocities. 

In  use,  and  knowing  approximately  the  velocity  to  be  given  the 
projectile,  the  pointer  is  adjusted  across  the  scale  so  as  to  intersect 
that  point  on  the  line  which  indicates  the  elevation  required  for  the 
expected  velocity.  Should  the  shot  fall  100  yards  short,  the  pointer 
is  readjusted  to  intersect  that  point  which  will  indicate  the  required 
increase  in  elevation. 

It  follows  that,  with  the  pointer  set  to  correctly  indicate  the  point 
in  the  6,000-yard  line  for  the  velocity  used,  if  the  wheel  be  rotated  so 
that  the  pointer  intersects  the  3,000-yard  line  it  indicates  the  correct 
elevation  for  that  range  for  the  same  velocity. 

Elevating  System. — Two  handwheels  are  attached  to  the  ends  of 
the  elevating  shaft,  to  be  manipulated  by  two  men  standing  on  the  gun 
platform,  one  at  each  wheel.  These  wheels  actuate  through  a  train  of 
bevel  and  spur  gearing,  a  forged-steel  elevating  screw  operating  the 
bronze  elevating  slide  nut.  This  slide  nut  actuates  the  elevating  slide, 
to  which  the  lower  end  of  the  elevating  arm  is  pivoted,  through  the 
medium  of  two  helical  springs,  interposed  to  relieve  the  arm  from  shock 
due  to  the  downward  thrust  when  firing  with  the  gun  elevated. 

Upon  this  carriage  no  separate  spring  buffer  stops  are  provided,  as 
the  buffer  springs  between  the  slide  and  nut  fulfill  the  requirements. 
At  the  limit  of  depression  of  the  gun  the  slide  strikes  a  positive  stop 
and  the  nut  is  stopped  by  the  spring;  at  the  limit  of  elevation  the  nut 
strikes  a  positive  stop  and  the  slide  is  stopped  by  the  spring. 

In  order  to  render  the  power  required  for  elevating  and  depressing 
as  nearly  equal  as  possible,  the  downward  thrust  of  the  elevating  screw 
in  depressing  is  borne  by  a  ball-thrust  bearing  placed  beneath  the  ele- 
vating-spur gear  and  inclosed  with  it  on  top  of  the  rear  transoms. 
When  depressing  the  gun  by  raising  its  breech  (during  which  opera- 
tion the  men  at  the  wheels  have  to  overcome  a  certain  preponderance, 
due  to  weight  of  elevating  arm,  etc.),  the  top  disk  of  the  ball  bearing 
rotates  with  the  elevating-spur  gear  upon  the  rolling  balls  and  the  fric- 
tional  work  to  be  overcome  is  reduced. 

When  elevating  the  gun  by  lowering  its  breech  the  preponderance 
above  mentioned  assists  instead  of  opposes  the  motion.  Therefore,  to 


ARMAMENT  213 

prevent  the  slide  from  running  down,  due  to  the  weight  upon  it,  during 
this  operation  as  well  as  in  firing,  the  top  disk  is  arranged  with  ratchet 
teeth  to  be  engaged  by  pawls,  which  prevent  its  rotating  in  the  direction 
for  elevating  by  locking  it  to  the  transom.  By  this  locking  device  the 
ball-thrust  bearing  is  thrown  out  of  action  when  elevating  and  the 
elevating-spur  gear  is  obliged  to  turn  on  a  bronze  washer  interposed 
between  it  and  the  fixed  top  disk  of  the  ball  bearing,  thus  increasing 
the  frictional  resistance  over  what  it  would  otherwise  have  been. 

Counterbalance  Device. — In  order  to  still  " further  equalize"  the 
power  required  for  elevating  and  depressing,  an  attachment  has  been 
designed  for  this  carriage,  called  a  "  counterbalance  device."  This  con- 
sists of  a  weight  hung  by  a  double  wire  rope  which  passes  over  pulleys 
and  is  attached  to  the  elevating  slide  nut  so  as  to  oppose  and  partially 
counterbalance  the  weight  of  the  slide  and  half  the  weight  of  the 
elevating  arm. 

The  use  of  too  much  balance  weight  will  result  in  an  upward  thrust 
on  the  elevating  screw,  conducing  to  serious  wear  on  the  under  side  of 
the  screw  bearing. 

Traversing  System. — For  pointing  in  azimuth  by  hand  power, 
two  crank  handles  may  be  attached  to  the  traversing  shaft  and  manipu- 
lated by  two  men  standing  on  the  working  platform,  one  at  each  crank. 
From  this  shaft  motion  is  transmitted  by  two  pairs  of  bevel  gears  to 
the  vertical  shaft  in  bearings  on  the  chassis  and  racer,  the  pinion  at  the 
lower  end  of  which  engages  in  the  circular  traversing  rack  bolted  to 
the  base  ring  and  by  its  .rotation  causes  the  racer  and  all  parts  carried 
thereon  to  rotate  upon  the  rollers  and  around  the  pintle  surface. 

While  the  construction  of  the  carriage  itself  permits  it  to  be  trav- 
ersed 360  degrees,  stops  are  provided  which  are  to  be  screwed  to  the 
inside  of  the  pintle  above  the  traversing  rack,  limiting  the  movement 
in  azimuth  as  may  be  required  by  the  emplacement  in  which  the  gun 
is  mounted. 

To  prevent  excessive  shocks  to  the  traversing  gearing  or  other  parts, 
due  to  striking  obstructions  or  to  too  sudden  application  of  power, 
etc.,  the  intermediate  bevel  gear  wheel  is  not  keyed  to  the  shaft,  but 
centered  upon  and  held  frictionally  by  three  disks,  free  to  move  longi- 
tudinally on  two  feathers  made  solid  on  the  pinion  shaft,  and  pinched 
between  a  solid  collar  above  and  an  adjusting  nut  below.  The  nut  is 
locked  by  being  jacked  apart  with  a  set  screw  at  a  cut  which  extends 
partly  across. 

The  friction  surfaces  are  provided  with  oil  grooves,  which  together 
with  the  spaces  between  the  disks,  are  to  be  kept  filled  full  with  oil 


214  THE  SERVICE  OF  COAST  ARTILLERY 

through  a  hole  in  the  top  end  of  the  shaft.  The  adjusting  nut  should 
be  set  up  just  enough  to  rotate  the  carriage  by  hand  without  slipping. 
It  is  intended  that  in  rotating  by  power  suddenly  applied  the  disks 
shall  slip  at  first,  and  thus  pick  up  the  load  gradually. 

Traversing  Brake. — In  a  convenient  position  on  the  racer,  outside 
of  the  left  chassis  and  near  the  azimuth  pointer  and  the  controller 
auxiliary  handle  is  the  traversing  brake.  This  consists  of  a  vertical 
guide  attached  to  the  racer,  in  which  slides  a  brake  clamp  with  a  toe 
designed  to  grip  under  the  lift  on  the  inside  of  the  pintle  when  pulled 
up  against  the  latter  by  the  brake  screw.  This  screw  is  threaded  into 
the  upper  end  of  the  brake  clamp  and  when  screwed  down  by  a  clock- 
wise motion  (as  viewed  from  above)  of  the  handle,  its  lower  end  bears 
upon  a  hardened  plate  upon  the  racer,  and  thus  draws  up  the  brake 
clamp  and  sets  the  brake.  A  notched  flange  on  the  upper  portion  of 
the  screw  bolt  enables  the  handle  to  be  set  at  a  convenient  position,  in 
which  it  is  retained  by  screwing  down  the  nut  above  it.  This  handle 
engages  under  a  spring  catch  in  its  "off"  position  to  keep  it  out  of  the 
way. 

Retracting  System. — For  hauling  the  gun  down  by  hand  two  re- 
movable crank  handles  may  be  attached  to  the  retracting  crank  shaft 
and  maneuvered  by  eight  men  standing  on  the  gun  platform,  four 
working  on  each  crank.  The  retracting  crank  shaft  actuates  through 
a  train  of  three  pairs  of  spur  gearing,  two  drums,  to  which  are  fastened 
by  corrugated  clamps  two  wire  clamps,  which  wind  upon  the  drums. 
A  ratchet  and  pawl  prevents  the  load  from  overhauling  the  gearing. 
From  the  drums  these  ropes  pass  around  guide  pulleys  in  rear  of  the 
recoil  buffers  and  are  hooked  to  the  upper  ends  of  the  gun  levers. 
These  ropes  remain  with  the  carriage,  and  when  not  in  use  are  wound 
upon  the  drums  until  the  ropes  project  but  a  short  distance  from  the 
guide-pulley  brackets. 

For  rapid  and  easy  overhauling  of  the  ropes,  two  small  speed  cranks 
are  fixed  to  the  crank  shaft  back  of  crank  handles.  To  save  time  these 
should  also  be  used  to  wind  up  the  slack  of  the  rope  before  placing  the 
crank  handles  on  the  shaft.  In  hauling  down,  care  should  be  exercised 
that  both  ropes  are  under  equal  tension. 

After  taking  up  the  slack  in  the  ropes  and  putting  some  strain  on 
them,  they  should  be  vibrated  slightly,  and  if  found  to  be  unequally 
loaded,  adjustment  should  be  made  at  the  rope  clamps  on  the  drums. 
After  the  loop  of  the  rope  is  placed  over  the  hook  on  the  gun  levers, 
and  while  winding  up  the  slack,  special  care  should  be  taken  that  the 
rope  is  guided  to  the  pulleys  without  any  kinks  or  any  slack  and  that 


ARMAMENT  215 

the  coils  lie  smoothly  upon  the  drums  without  crossing  the  ridges  be- 
tween the  grooves. 

On  account  of  the  extra  counterweight  used  to  decrease  the  time  of 
going  into  battery,  the  operation  of  retraction  requires  the  application 
of  considerably  more  power  than  would  otherwise  be  the  case.  Retrac- 
tion by  hand  power  will,  therefore,  be  found  somewhat  difficult.  This 
is,  however,  not  expected  to  be  objectionable,  as  retraction  by  the 
electric  motor  supplied  is  regarded  as  the  normal  practice,  retraction 
by  hand  being  provided  for  use  principally  in  case  of  trouble  with  the 
electrical  plant. 

In  case  retraction  by  hand  is  desired  to  be  habitually  used,  as  for 
example  during  the  drill  season,  the  amount  of  counterweight  may  be 
reduced  to  about  158,000  pounds  for  use  with  the  gun  of  the  model  of 
1900,  or  to  about  135,000  pounds  for  use  with  the  gun  of  the  model  of 
1895.  With  these  reductions  in  the  counterweight,  the  time  required 
for  the  gun  to  go  into  battery  will  be  increased  to  about  twelve  or 
thirteen  seconds. 

Retracting  Gear,  Clutch,  and  Brake. — To  permit  the  most  rapid 
•overhauling  of  the  wire  ropes  possible  there  has  been  added  a  spring- 
engaging  claw  clutch  for  rotating  the  drum  shaft  from  the  drum  gear 
in  retracting.  With  the  clutch  thrown  off,  the  ropes  can  be  drawn  out 
•quickly,  revolving  the  drums  Lnd  shaft  rapidly  in  the  drum  gear. 

In  order  to  prevent  overrunning  and  injury  to  the  ropes  a  band 
brake  is  added,  gripping  the  hub  of  the  left  drum  upon  lifting  a  crank 
handle.  The  clutch  is  thrown  off  by  drawing  a  loop  handle  on  the  left 
side  until  the  feathers  are  drawn  out  and  permit  the  handle  to  be  given 
a  quarter  turn,  which  locks  the  clutch  off  with  the  spring  compressed. 

When  enough  rope  is  overhauled  the  brake  handle  is  raised  to  stop 
the  shaft,  the  loop  is  given  a  quarter  turn  back  to  permit  the  feathers 
to  enter,  and  the  spring  moves  the  clutch,  on  its  feathers  in  the  drum 
shaft,  to  engagement. 

Working  Platform. — The  outside  platform  of  plates  and  angles  is 
flush  with  top  of  racer,  is  supported  on  radial  cast-steel  brackets  bolted 
to  it,  and  covers  the  recess  around  the  turntable  flush  with  the  fixed 
part  of  the  platform. 

The  inside  platforms,  supported  by  the  racer  and  chassis,  cover  the 
sides  of  the  counterweight  well.  On  the  right  side  a  manhole  and 
ladder  are  provided  for  entering  the  well. 

Sighting  Standards  and  Platforms. — These  platforms  of  plates 
and  angles  extend  along  each  side  of  the  carriage,  supported  in  front 
by  brackets  bolted  to  the  top  of  the  crosshead  guides  on  the  chassis  and 


216  THE  SERVICE  OF  COAST  ARTILLERY 

in  rear  by  standards  bolted  to  the  racer  and  chassis.  The  brackets  and 
standards  are  of  steel  castings. 

A  flight  of  steps  is  provided  at  the  front  and  rear  end  of  each  plat- 
form. Hand  rails  and  a  screen  to  protect  the  gunner's  body  from  the 
elevating  arm  during  recoil  of  the  piece  are  also  provided.  These 
platforms  furnish  not  only  a  station  for  sighting  and  pointing  and 
firing  (by  electrical  power),  but  also  a  convenient  means  of  access  to 
the  gun,  retracting  hooks,  trunnion  beds,  etc.,  for  oiling  or  other  pur- 
poses, e.  g.,  for  inserting  a  new  primer. 

Sight  Standard. — This  standard  is  a  steel  casting,  seated  and 
clamped  in  a  split  socket  in  the  top  of  the  left  standard.  It  extends 
forward  as  a  bracket,  forming  a'  pivot  and  guide  for  the  sight  arm 
which  carries  the  combined  bar  sight  with  the  new  3-inch  telescope. 
The  pivot  is  at  such  height  that  the  sight  lines  may  be  depressed  6 
degrees  if  necessary,  when  firing  gun  at  5  degrees  depression,  and  still 
pass  over  the  crest  of  the  parapet. 

Counter-set  screws  are  provided  at  the  socket  for  making  a  slight 
adjustment  in  rotation  and  in  fixing  the  standard,  the  line  of  collima- 
tion  of  the  telescope  and  open  sights  in  a  vertical  plane,  parallel  to  a 
vertical  plane  through  the  axis  of  gun. 

To  this  standard  is  also  attached  the  bracket  supporting  the  con- 
troller extensions  and  handles,  the  firing  pistol,  and  the  box  protecting 
the  rheostats  for  adjusting  the  lights  which  illuminate  the  sight  grad- 
uations. 

For  use  on  the  right  trunnion,  the  telescope  sights  in  service  are  the 
models  of  1896  Mi,  of  1897,  of  1898,  and  of  1898  M,  described  in 
Chapter  VII. 

Sight-Laying  Mechanism. — A  pair  of  bevel  gears  transmits  the  rota- 
tion of  the  elevating-wheel  shaft  to  the  sight-elevating  screw,  which, 
working  in  a  threaded  bearing  in  the  sight-elevating  slide,  causes  the 
latter  to  move  up  or  down  in  a  guideway  formed  upon  the  rear  of  the 
left  standard  near  its  base.  To  this  slide  is  pinned  the  lower  end  of 
the  sight-elevating  arm,  which  is  partly  inclosed  in  the  standard,  and 
to  the  upper  end  of  which  is  pivoted  the  rear  end  of  the  parallel  arm 
and  the  lower  end  of  the  sight-arm  link. 

To  the  upper  end  of  the  sight-arm  link  is  pivoted  the  rear  end  of 
the  sight  arm.  The  front  sight  arm  and  the  parallel  arm  being  of  the 
same  length  between  centers  of  pivot  holes  and  their  front  ends  being 
pivoted  in  fixtures  attached  to  the  standard,  and  these  pivots  being  at  a 
distance  from  each  other  equal  to  the  length  of  the  sight-arm  link,  a 
true  parallel  motion  is  secured  between  these  two  arms;  and  the  sight- 


ARMAMENT  217 

elevating  arm  and  gearing  are  so  proportioned  that  each  of  these  arms 
is  kept  always  at  the  same  angle  of  elevation  as  the  axis  of  the  gun. 
The  sight-arm  link  is  inclosed  in  the  standard,  and  the  parallel  arm  is 
in  a  bracket,  attached  to  the  standard,  which  protects  it  but  which  is 
open  at  the  top. 

The  sight-elevating  screw  is  not  solid  with  or  keyed  to  the  bevel 
gear  by  which  it  derives  rotation  from  the  elevating  shaft,  but  is  fric- 
tionally  held  thereto  by  the  pulling  down  of  its  cone  head  into  a  friction 
seat  in  that  gear  by  a  nut  on  the  screw,  which,  through  a  washer,  presses 
against  a  bushing,  which,  in  turn,  presses  against  the  bottom  of  the  gear. 
The  washer  has  a  feather  entering  a  slot  in  the  screw,  to  insure  its  rota- 
tion with  it.  The  nut  is  slit  half  through  transversely  and  furnished 
with  a  set  screw  to  permit  jamming  it  on  the  threads  after  the  screw  is 
adjusted.  After  loosening  the  nut,  the  sight-elevating  screw  may  be 
freed  from  its  gear  and  rotated  by  the  hexagon  lower  end,  and  the 
sight-elevating  gearing  thus  be  moved,  for  adjustment,  independently 
of  the  gun-elevating  mechanism. 

The  parallel  arm  has  a  true  upper  surface  which  furnishes  a  seat  for 
a  level  for  testing  horizontality  thereof.  The  parallel  arm  is,  for  this 
reason,  also  placed  at  a  convenient  height  for  a  man  standing  on  the 
gun  platform.  After  adjusting  the  parallel  arm  to  be  horizontal  when 
the  gun  is  horizontal,  the  nut  on  the  sight-elevating  screw  should  be 
screwed  up  tight  against  the  washer,  bushing,  and  gear,  while  motion 
of  the  screw  is  prevented  by  a  wrench  applied  to  its  lower  end.  The 
nut  should  then  be  jammed  by  its  set  screw. 

By  these  means  the  bevel  gear  is  firmly  held  to  the  sight-elevating 
screw,  and  any  motion  of  the  elevating  slide,  being  accomplished  by  a 
rotation  of  the  elevating  shaft,  produces  through  this  bevel  gear  and 
its  mate  a  rotation  of  the  sight-elevating  screw,  which,  in  turn,  causes 
the  sight-elevating  slide  to  move  in  the  same  direction  as  the  elevating 
slide.  Thus  the  sight-elevating  arm  is  moved  up  or  down,  causing  in 
the  parallel  arm  and  sight  arm  an  angular  movement  the  same  as  the 
movement  produced  in  the  gun  itself. 

In  the  final  adjustment  of  the  combined  telescopic  and  bar  sight  the 
horizontality  of  the  parallel  arm  may  be  slightly  disarranged. 

Lanyard  Safety  Attachment. — This  is  to  prevent  the  firing  of  the 
piece  by  a  pull,  accidental  or  otherwise,  upon  the  lanyard  before  the 
gun  has  risen  to  the  firing  position;  that  is,  before  it  has  been  raised 
to  such  a  height  that  the  projectile  will  clear  the  parapet.  It  consists 
of  an  incased  reel,  attached  to  the  elevating  band,  upon  which  a  short 
cable  is  automatically  wound  by  a  spiral  spring,  and  locked,  except 


218  THE  SERVICE  OF  COAST  ARTILLERY 

when  piece  is  in  battery,  by  a  ratchet  and  pawl.  One  end  of  a  short 
lanyard  is  hooked  to  the  primer  and  the  other  to  the  end  of  this  cable. 
The  long  lanyard  in  the  hands  of  the  cannoneer  is  also  hooked  to  this 
cable.  A  pull  on  the  lanyard,  when  gun  is  out  of  battery,  cannot 
unwind  the  cable,  pull  the  short  lanyard,  or  fire  the  primer.  When 
gun  rises  in  battery,  a  cam  on  the  elevating  band  passing  under  the 
pawl  lifts  it  out  of  engagement  with  the  reel,  which  can  then  be  un- 
wound, permitting  the  primer  to  be  fired. 

The  initial  tension  of  spring  should  be  sufficient  only  to  wind  up  the 
cable  with  lanyards  attached.  It  may  be  adjusted  by  loosening  the 
nut  on  the  spring  shaft  and  with  wrench  on  the  squared  end  of  shaft 
(projecting  from  the  center  of  the  case)  withdraw  the  locking  pin  and 
wind  up  or  unwind  the  spring,  returning  the  locking  pin  to  one  of  the 
quarter-turn  positions  and  tightening  nut. 

Electric  Safety-Firing  Attachments. — The  carriage  is  arranged 
to  permit  electric  firing  either  individually  (by  a  key  on  the  sighting 
platform  or  one  on  the  working  platform)  or  in  salvo  (by  a  key  in  the 
battery  commander's  station).  To  arrange  for  firing  by  whichever  of 
these  methods  is  desired,  a  double-pole,  double-break,  double-throw 
switch  in  the  Signal  Corps'  outlet  box  is  turned  to  the  proper  [indicated] 
position.  This  connects  with  a  source  of  electrical  power  two  of  the 
four  wires  from  this  switch  to  the  carriage,  namely,  either  the  two 
wires  tapped  directly  into  power  mains  in  the  emplacement  (for  indi- 
vidual or  "  gun  "  fire)  or  the  two  wires  leading  back  through  the  battery 
commander's  firing  key  to  the  power  mains  (for  battery  or  salvo  fire). 
The  latter  two  wires  are  led  without  any  interrupting  switch  or  key  to 
the  "safety-firing  switch"  on  the  left  chassis  (connecting  with  the 
front  lug  of  the  top  carriage). 

The  former  two  wires  are  broken  at  the  two  firing  keys  on  the  car- 
riage in  such  manner  that  the  closing  of  either  key  closes  the  circuit; 
they  then  go  to  the  safety-firing  switch.  This  switch  is  designed  to 
break  the  firing  circuit  automatically  as  soon  as  the  top  carriage  has 
recoiled.  The  firing  circuit  cannot  be  reclosed  at  this  point  until  the 
top  carriage  returns  to  battery  (within  2.5  inches  of  its  prescribed  firing 
position).  The  circuit  is  even  then  not  reclosed  automatically,  but  is 
to  be  closed  by  the  intentional  act  of  a  cannoneer  after  the  gun  is  laid 
and  otherwise  ready  to  fire.  Thus  the  battery  commander  cannot 
fire  the  gun  before  the  gun  commander  has  completed  the  laying,  etc., 
and  is  ready. 

However,  as  it  may  be  desirable  in  firing,  piece  by  piece,  to  obtain 
the  maximum  rapidity  of  action  by  firing  immediately  the  gun  comes 


ARMAMENT  219 

into  battery,  the  switch  is  so  arranged  that  it  may  be  set  to  make  con- 
tact automatically  when  the  top  carriage  is  in  battery.  Then  the  piece 
can  be  fired  by  pressure  of  one  of  the  firing  keys.  This  must  never 
be  so  set,  however,  for  battery  fire,  as  a  shot  might  be  lost  or  someone  hurt 
by  the  battery  commander  firing  after  the  gun  was  in  battery  but  before 
it  was  properly  laid  or  before  all  cannoneers  were  in  safe  positions. 
This  setting  for  automatic  action  should  never  be  made  except  by  express 
order. 

The  Safety-Firing  Switch  is  essentially  a  double-pole,  single-brake, 
single-throw  knife  switch,  the  body  carrying  the  two  knife  blades  being 
pivoted  to  the  chassis  and  the  double  blades,  or  sockets  for  the  knives 
to  make  contact  with,  being  fastened  to  the  lug  of  the  top  carriage. 
When  the  top  carriage  is  in  battery  the  sockets  are  directly  above  the 
knife  blades,  and  if  the  body  is  raised  by  hand  until  the  blades  engage 
in  them  the  circuit  will  be  closed  at  this  point,  and  the  spring  grip  of 
the  sockets  upon  the  blades  will  support  the  weight  of  the  body  and 
keep  the  contact  made  until  the  top  carriage  moves  to  the  rear  and 
releases  the  blades,  when  the  body  will  swing  downward  about  its  pivot 
on  account  of  its  own  weight. 

As  long  as  the  top  carriage  is  not  in  battery  it  is  evident  that  con- 
tact cannot  be  remade,  since  the  sockets  are  not  within  reach  of  the 
knife  blades.  Even  when  the  top  carriage  returns  to  battery  there  is 
no  tendency  of  the  body  to  rise  (against  its  own  weight)  and  make 
contact,  so  that  it  must  be  lifted  by  a  man. 

The  automatic  remaking  of  contact  is  secured  when  ordered  by 
raising  the  support  which  holds  the  body  always  in  its  upper  position, 
in  which  case  the  blades  will  engage  in  the  sockets  as  the  top  carriage 
comes  into  battery. 

Electric  Motor  Equipment. — The  carriage  is  provided  with  a  com- 
plete electric  motor  equipment.  This  consists  essentially  of  a  motor, 
with  its  controller  and  other  adjuncts,  for  traversing  the  carriage,  and 
another  motor,  with  its  controller  and  other  adjuncts,  for  either  retract- 
ing or  elevating  and  depressing,  according  to  whether  the  maneuver 
lever  is  set  to  throw  the  idler  gear  carried  by  it  into  mesh  with  the  gear 
on  the  retracting  .or  that  on  the  elevating  shaft. 

The  motors  are  of  the  completely  inclosed  type,  supported  by  cast- 
steel  brackets  bolted  to  the  inner  side  of  the  left  chassis. 

The  traversing  motor  has  a  pinion  upon  its  shaft  which  engages 
directly  with  a  gear  upon  the  traversing  crank  shaft.  There  is  no  means 
of  throwing  this  gear  out  of  mesh,  and  consequently  the  motor  arma- 
ture rotates  when  the  carriage  is  traversed  by  hand. 


220  THE  SERVICE  OF  COAST  ARTILLERY 

The  elevating  and  retracting  motor  shaft  extends  through  a  bearing 
in  the  opening  in  the  chassis,  and  in  an  improved  design  is  supported 
at  its  outer  end  by  a  bracket  bearing.  A  cast-steel  maneuvering  lever 
is  arranged  to  oscillate  on  the  motor  shaft  and  to  carry  an  idler  gear 
on  a  fixed  pin  and  in  mesh  with  the  motor  pinion,  between  its  branches. 
The  top  end  of  the  lever  is  guided  in  and  may  be  pinned,  in  three 
different  positions,  to  an  arc  attached  to  the  chassis  over  the  motor 
shaft. 

With  the  lever  in  the  forward  position  the  idler  is  in  mesh  with  a 
gear  on  the  retracting  crank  shaft,  in  which  case  the  motor  will  retract, 
and  with  the  lever  in  the  rear  position  the  idler  meshes  with  the  gear 
on  the  elevating- wheel  shaft  and  the  motor  elevates  or  depresses  the  gun. 
When  pinned  in  the  mid  position  the  idler  is  free  from  both  gears  and 
the  motor  armature  will  not  be  revolved  by  elevating  or  retracting  by 
hand. 

This  lever  also  throws  the  commutation  switch  so  that  in  retracting 
two  rheostats  in  multiple  enable  the  motor  to  do  more  work  than  when 
elevating  or  depressing  the  gun. 

The  lever  should  never  be  left  unpinned,  and  should  never  be  shifted 
when  the  motor  or  any  part  of  the  gearing  is  in  motion.  Care  should 
be  taken  in  shifting  that  the  teeth  of  the  idler  are  opposite  spaces  in  the 
gears. 

The  two  controllers,  one  for  the  traversing,  one  for  the  elevating- 
retracting  motor,  are  placed  side  by  side  on  a  frame  bolted  to  the 
working  platform  immediately  in  rear  of  the  left  standard.  By  turn- 
ing the  shafts  of  these  controllers  by  the  handles  provided,  the  elec- 
trical connections  within  are  changed  in  such  combinations  as  to  start, 
stop,  and  give  the  different  speeds  of  motion  provided  for.  When 
turned  to  the  off  position  the  connections  are  so  arranged  that  a  short 
circuit  is  made  from  brush  to  brush,  thus  closing  the  circuit  through 
the  armatures  of  the  motors  while  the  field  magnets  remain  energized. 
Forced  rotation  of  the  armatures  then  cause  the  motors  to  work  as 
generators,  which  requires  that  work  to  be  done  by  the  force  which 
rotates  them.  The  motors  under  these  circumstances  are  therefore  brakes. 

This  brake  effect  does  not  become  operative  in  the  elevating-retract- 
ing motor  until  the  controller  reaches  the  off  position,  so  that  if  the 
handle  be  turned  quickly  to  that  position  while  the  gearing  is  running 
at  full  speed  the  motor  armature  would  be  rotated  rapidly  and  the 
strains  due  to  the  brake  action  would  be  severe.  The  traversing  motor, 
however,  does  operate  as  a  brake  to  reduce  the  speed  of  traversing  when- 
ever the  controller  handle  is  turned  toward  the  off  position — that  is, 


ARMAMENT  221 

whenever  the  controller  is  set  to  a  slower  speed  than  that  at  which  the 
motor  is  running..  This  is  due  to  the  fact  that  this  motor  has  a  cur- 
rent of  variable  voltage  supplied  to  it,  the  voltage  determining  the  rate 
at  which  the  motor  runs  as  a  motor.  If  the  motor  be  actually  running 
at  a  higher  speed  than  that  for  which  the  controller  is  set,  its  counter 
electromotive  force  exceeds  the  impressed  voltage,  thereby  generating 
a  current  which  tends  to  reverse  the  direction  of  rotation  of  the  gener- 
ator— that  is,  to  drive  it  as  a  motor.  This,  of  course,  requires  work  to 
be  done  by  the  force  tending  to  rotate  the  traversing  motor  at  the 
higher  speed,  and  as  this  force  is  the  inertia  of  the  moving  carriage, 
the  result  is  that  the  speed  is  slowed  down  by  this  braking  action. 
Therefore,  when  the  controller  comes  to  the  off  position  the  carriage 
should  have  less  remaining  velocity  to  be  overcome  by  the  brake  effect 
of  the  motor  when  short-circuited  than  would  otherwise  be  the  case, 
and  the  carriage  therefore  is  brought  to  rest  more  promptly  and  at  the 
same  time  with  less  strain.  To  secure  the  full  effect  of  this  action  the 
controller  handle  should  be  turned  rather  slowly,  so  that  the  retarding 
brake  action  may  be  of  some  duration. 

The  elevating-retracting  controller  has  wired  between  it  and  the 
motor  a  commutation  switch,  automatically  set  by  throwing  the  maneu- 
ver lever,  so  that  when  elevating  or  depressing,  the  upper  rheostat 
only  is  inserted,  permitting  the  motor  to  operate  at  4  horsepower,  and 
when  retracting  the  second  rheostat  is  thrown  in  multiple  with  the 
first,  thus  permitting  the  motor  to  operate  at  8  horsepower. 

Resting  upon  the  squared  upper  end  of  the  shaft  of  each  controller 
is  a  shaft  called  the  "  controller  extension,"  which  reaches  to  a  con- 
venient height  above  the  sighting  platform  and  has  its  upper  end  squared 
to  receive  the  controller  handle  and  thus  permit  rotation  of  the  con- 
troller shaft,  and  operation  of  the  motor,  from  the  sighting  platform. 
This  controller  extension  may  be  lifted  without  releasing  any  catch, 
and  the  controller  handle  may  be  put  upon  the  squared  upper  end  of 
the  controller  shaft  for  operation  from  the  gun  platform. 

In  addition  to  the  above,  the  traversing  controller  has  its  shaft 
connected  by  two  pairs  of  bevel  gears  to  a  short  vertical  shaft  on  the 
racer  near  the  azimuth  pointer.  The  handle  may  be  placed  on  this 
shaft  and  the  traversing  controller  operated  from  this  point  when  it  is 
Desired  to  lay  the  gun  to  a  given  azimuth  by  the  scale  and  pointer 
(Case  III).  Only  one  set  of  controller  handles  is  provided  (that  is,  one 
handle  for  each  of  the  two  controllers),  and  are  marked  to  show  the 
direction  in  which  the  handle  should  be  moved  to  produce  motion  in 
the  direction  stated.  The  hand  of  the  operator  indicates  the  direction 


222  THE  SERVICE  OF  COAST  ARTILLERY 

of  motion  and  may  be  regarded  as  the  pointer.  (To  simplify  the  action 
as  much  as  possible  the  direction  of  motion  of  the  handle  of  the  travers- 
ing controller  is  the  same  as  the  motion  of  the  gun) . 

The  farther  the  handles  are  moved  from  the  "off"  position  the 
greater  is  the  resulting  speed.  As  any  mass  acted  on  by  a  force  re- 
quires time  to  acquire  its  maximum  velocity,  so  the  carriage  requires 
a  short  time  to  acquire  the  velocity  corresponding  to  any  position  of  the 
handles.  It  is  well,  therefore,  to  move  the  handles  somewhat  slowly 
in  changing  speed  to  avoid  getting  up  more  speed  than  is  desired. 
Too  sudden  turning  of  the  handle,  moreover,  imparts  a  greater  acceleration 
and  correspondingly  severe  strain  upon  all  parts.  It  may  result  in  break- 
age, and  is  very  apt  to  cause  opening  of  circuit  breakers  (due  to  over- 
load), which  will  mean  a  short  delay  to  close  them,  which  may  be  of 
importance  in  action  or  target  practice. 

There  are  two  circuit  breakers  on  the  carriage,  one  for  each  motion, 
placed  in  an  iron  box  bolted  to  the  under  side  of  the  rear  projection  of 
the  left  chassis.  They  are  capable  of  adjustable  setting,  and  should  be 
set  to  open  at  about  40  amperes  for  the  traversing  and  about  70  am- 
peres for  the  elevating  retracting  motor.  Any  electrician  sergeant  will 
understand  how  to  set  them.  When  a  circuit  breaker  opens  on  account 
of  overload,  the  handle  swings  over  from  the  right  to  the  left,  the  circuit 
is  broken,  and  no  current  can  pass.  To  reclose  the -breaker  remake  the 
circuit,  and  allow  the  current  to  pass  again — simply  move  this  handle 
back  to  the  right. 

If  the  carriage  were  traversed  up  to  the  positive  stops  at  high  speed 
with  electric  power,  damage  would  probably  result.  To  prevent  this 
an  automatic  traversing  controller  stop  is  provided.  A  cam  is  bolted 
to  the  base  ring  near  the  extreme  limit  of  traversing  "muzzle  right/' 
which,  when  struck  by  the  lt  shipper  "  (an  arm  fixed  to  the  shaft  carried 
by  the  racer),  presses  this  shipper  gradually  outward  in  such  manner 
that,  by  suitable  gear  connections,  the  traversing  controller  shaft  is 
gradually  turned  to  the  off  position.  Thus  the  speed  of  the  carriage 
is  reduced  and  the  traversing  is  finally  stopped.  By  shifting  the  cam 
until  the  correct  position  is  found  the  carriage  may  be  traversed  at 
full  speed  to  the  stop,  and  will  come  to  rest  very  close  to  the  extreme 
position  allowable.  Once  set  by  the  Ordnance  Department,  this  cam 
should  not  be  shifted.  A  similar  cam  actuating  another  shipper  on  the 
same  shaft  limits  the  left  traversing.  In  spite  of  these  safety  stops 
it  is  recommended  to  slow  the  carriage  down  as  it  approaches  the  end  of 
its  allowed  motion. 

No  such  safety  stops  are  provided  for  the  elevating,  depressing,  or 


ARMAMENT  223 

refracting  on  account  of  the  complication  involved  and  the  smaller 
necessity  existing.  In  these  operations  safety  and  proper  action  will 
depend  upon  that  proper  care  in  manipulation  which  all  machines 
should  receive.  At  the  same  time,  should  these  motions  accidentally 
be  continued  until  the  limiting  positive  stops  are  struck,  it  is  probable 
that  nothing  more  serious  than  opening  of  the  circuit  breaker  would 
result. 

A  detailed  description  of  the  electrical  equipment  furnished  by  the  man- 
ufacturers should  be  studied  by  those  in  charge.  It  will  be  found  to 
relate  more  particularly  to  the  electrical  features  of  the  equipment,  those 
with  which  the  officer  in  charge  of  the  post  electrical  plant  and  his  assist- 
ants are  principally  concerned,  while  the  above  notes  have  dealt  with 
mechanical  features  and  with  appliances  and  operations  with  which  the 
officer  in  charge  of  the  armament  and  the  gunner  and  cannoneers 
operating  the  carriage  are  most  directly  concerned. 

The  following  data  and  suggestions  relative  to  operation  of  the 
motor  equipment,  as  well  as  those  heretofore  mentioned  incidentally 
to  the  description,  are  based  upon  the  experience  so  far  had  with  these 
equipments,  and  are  subject  to  revision  in  the  light  of  more  extensive 
experience,  but  will  be  found  useful  as  guides  to  the  proper  use  and 
care  of  the  equipment,  and  as  criteria  for  judging  its  condition: 

(a)  There  is  nothing  to  prevent  the  running  of  both  motors  simul- 
taneously.    If  the  power  supply  is  inadequate,  this  will  simply  result 
in  diminution  of  speed. 

(b)  Hand  cranks  should  be  removed  from  shafts  when  operating  elec- 
trically, as  they  rotate  at  considerable  speed  and  might  injure  cannon- 
eers getting  within  reach  of  them. 

(c)  Especial  care,  should  be  taken  to  keep  all  bearings  and  gears  con- 
nected with  the  system  well  oiled  (oil  before  each  drill,  without  fail)  ; 
but  the  amatures,  field  coils,  and  conductors  should  be  kept,  as  far  as 
possible,  free  from  oil,  which  injures  their  insulating  material. 

(d)  Sparking  at  commutators  and  other  contacts  should  be  promptly 
investigated  by  an  electrician  and  corrected  if  possible. 

(e)  Care  should  be  taken  that  the  commutator  brushes  on  all  machines 
are  set  with  the  proper  lead.     Generally  these  are  set  once  for  all,  and 
care  is  only  necessary  to  see  they  are  not  shifted. 

(/)  Avoid  injury  to  machines  and  conductors  by  blows  from  tools, 
cannoneers'  feet,  etc. 

(g)  Do  not  turn  the  controller  handles  on  or  off  suddenly.  They 
may  be  shifted  with  considerable  rapidity,  but  all  manipulation  should 
be  gentle  and  easy. 


224  THE  SERVICE  OF  COAST  ARTILLERY 

(h)  Avoid  running  past  the  desired  setting.  It  is  easier  and  quicker 
to  stop  a  little  short  and  perfect  the  setting  by  successive  small  move- 
ments. 

(i)  Very  small  movements  may  be  obtained  by  turning  the  con- 
troller handles  slightly  from  the  off  position  and  then  turning  back 
immediately  to  the  off  position. 

(/)  Avoid  running  clear  up  to  the  limits  of  allowed  movement, 
especially  at  the  higher  speeds. 

(k)  Always  have  the  circuit  breakers  on  the  carriage  set  to  open 
at  a  lower  current  than  the  corresponding  breakers  on  the  switch-board 
panel.  The  breakers  on  the  carriage  are  put  there  to  permit  reclosing 
with  the  least  loss  of  time,  and  to  avoid  the  necessity  of  communicating 
with  the  man  in  charge  of  the  panel  and  motor-generator  set,  which 
will  be  installed  under  cover  at  a  distance. 

(/)  See  that  all  binding  posts  are  tightly  set  to  insure  good  con- 
tacts. 

(m)  All  operations  should  be  performed  as  frequently  as  possible 
to  keep  all  components  in  proper  running  order  and  to  familiarize  the 
personnel  therewith  and  enable  them  to  gain  that  facility  of  handling 
without  which  much  of  its  efficiency  and  usefulness  will  be  sacrificed. 

In  regard  to  the  motor-generator  set  and  switch-board  panel: 

(a)  Follow  carefully  the  directions  for  putting  this  system  into 
action. 

(6)  Watch  the  circuit  breakers,  and,  if  either  opens,  close  it  promptly 
in  order  to  avoid  delays  in  the  service  of  the  piece. 

(c)  Measure  the  speed  of  the  motor-generator  set  from  time  to  time 
to  insure  that  it  is  running  properly 

(d)  Supply  as  nearly  constant  voltage  to  this  set  as  possible,  in 
order  that  its  speed  and  the  voltage  supplied  by  it  to  the  traversing 
motor  may  be  as  calculated.     Otherwise,  the  speeds  of  the  carriage 
will  not  be  as  calculated. 

((?)  Take  frequent  reading  of  the  voltage  and  amperage  shown  by 
the  instruments  on  the  switch-board,  and  keep  as  full  record  as  prac- 
ticable of  these  readings  with  note  of  attendant  circumstances.  These 
records  should  always  show  the  voltage  correspondingly  in  time  to  the 
amperage  entered. 

(/)  The  motor-generator  set  running  light  (switch  to  carriage  open) 
should  require,  on  a  110- volt  circuit,  about  6  amperes.  The  speed 
should  be  1650  revolutions  per  minute. 

(g)  The  voltage  and  current  supplied  by  this  set  to  the  traversing 
motor  are  variable,  being  controlled  by  the  traversing  controller, 


ARMAMENT  225 

and  should  range  from  0  to  110  volts  with  current  from  12  to  25 
amperes. 

While  starting  or  accelerating  speed,  the  current  may  be  expected 
to  run  up  to  40  or  50  amperes,  occasionally. 

(h)  The  voltmeter  on  the  switch-board,  as  installed  in  the  earlier 
carriages,  does  not  measure  this  voltage,  but  the  line  voltage — that 
supplied  to  the  motor-generator  set  and  to  the  elevating-retracting 
motor.  To  measure  the  voltage  given  out  by  this  set  it  will  be  necessary 
to  change  the  connections  of  this  meter  or  to  connect  a  portable  volt- 
meter across  the  terminals  of  the  generator  of  the  set.  In  later  carriages 
the  voltmeter  will  have  a  double-throw  switch,  enabling  it  to  be  thrown 
into  either  circuit  desired.  This  modification  is  to  be  made  for  the 
earlier  carriages. 

(i)  The  voltage  of  the  current  supplied  to  the  elevating  and  retract- 
ing motor  is  that  of  the  line,  generally  110  volts.  The  amperage  should 
vary  between  10  and  20  amperes  for  elevating  and  20  to  30  amperes 
for  depressing  (if  no  counterbalance),  and  should  average  45  to  55 
amperes  for  retracting  with  164,500  pounds  counterweight  and  model 
of  1900  gun  (near  commencement  but  after  fairly  under  way)  and  be 
about  5  amperes  higher  near  the  termination  of  retraction.  For  6,000 
pounds  less  counterweight  the  current  for  retracting  is  about  15  am- 
peres less.  There  will  be  a  temporary  current,  considerably  higher, 
while  the  first  resistance  to  starting  from  rest  is  being  overcome.  With 
a  gun  of  the  model  of  1895  the  power  for  elevating  and  retracting  is 
about  as  above.  With  this  gun  and  142,000  pounds  counterweight, 
retraction  requires  30  to  40  amperes,  and  with  137,000  pounds  counter- 
weight about  25  to  35  amperes. 

In  regard  to  traversing: 

(a)  With  the  gear  ratio  applied  to  the  earlier  carriages  the  carriage 
may  be  traversed  at  maximum  speed  at  the  rate  of  one  revolution  in 
about  one  to  one-and-a-quarter  minutes,  and  at  minimum  speed  corre- 
sponding to  one  revolution  in  fifty  to  fifty-five  minutes.  As  the  above 
maximum  is  unnecessarily  rapid  and  the  minimum  not  as  slow  as 
-desirable,  an  increase  in  the  gear  ratio  is  to  be  made  which  will  give  a 
maximum  speed  corresponding  to  one  revolution  in  two  minutes  (en- 
abling the  sight  line  to  follow  a  vessel  traveling  about  50  miles  per 
hour  at  500  yards  range)  and  a  minimum  continuous  speed  of  one  rev- 
olution in  seventy  minutes  (enabling  the  sight  line  to,  follow  a  vessel 
traveling  about  9  miles  per  hour  at  3,000  yards  range).  Moving  tar- 
gets with  slower  angular  velocity  may  be  readily  followed  without 
.appreciable  error  by  successive  movements  of  the  controller  handle  to 


226  THE  SERVICE  OF  COAST  ARTILLERY 

the  minimum-speed  position,  bringing  it  back  immediately  to  the  off 
position.  Practice  will  develop  great  facility  in  this  respect. 

In  regard  to  elevating  and  depressing: 

(a)  Care  should  be  taken  in  these  operations  not  to  approach  the 
limits  of  movement  at  high  rate  of  speed.  By  slowing  down,  the  full 
limits  of  movement  may  be  attained  without  risk. 

(6)  The  gun  may  be  elevated  from  —  5  to  +10  degrees  in  about 
thirty-five  seconds. 

(c)  The  gun  may  be  depressed  from  +10  to  — 5  degrees  in  about 
thirty-five  seconds. 

(d)  The  above  times  are  the  results  of  trials  with  the  model  of  1900 
gun;  for  the  model  of  1895  gun  they  are  about  the  same. 

(e)  These  times  are  subject  to  considerable  variation,  as  they  include 
the  time  required  to  get  up  speed  and  to  slow  down.     They  are  only 
approximate. 

In  regard  to  retracting: 

(a)  The  model  of  1900  gun  with  164,700  pounds,  or  the  model  of 
1895  with  146,000  pounds,  of  counterweight  can  be  retracted  in  about 
two  and  three-fourths  to  three  minutes. 

(b)  With  about  5,000  pounds  less  of  counterweight  in  either  case  the 
gun  can  be  retracted  in  about  the  same  time. 

(c)  In  starting  retraction,  turn  the  controller  handle  slowly,  in  order 
that  the  starting  strains  and  current  be  not  unnecessarily  high. 

(d)  Be  careful  not  to  retract  so  far  that  the  gun  levers  strike  the 
recoil  buffers. 

(e)  Do  not  allow  the  gun  to  go  into  battery  with  the  ropes  attached. 
The  excessive  moment  of  the  heavy  counterweight  produces  an  unde- 
sirably high  velocity  of  rotation  of  the  gearing  and  motor  armature. 

Conduits,  Wiring,  and  Illumination.  —  Incandescent,  16-candle 
power  lamps  of  standard  form  are  provided  for  the  general  illumination 
of  the  carriage ;  8-candlepower  candelabra  lamps  are  provided  for  the 
scales  and  pointers  and  throttling  valves,  and  2-candlepower  miniature 
lamps  are  furnished  with  the  new  bar  sight  to  illuminate  the  scales  and 
the  reticule  inside  of  the  telescope.  All  lamps  are  shaded  so  as  to 
illuminate  only  the  parts  intended.  The  azimuth  and  elevation 
pointer  lamps  are  lighted  by  one  key;  the  lamps  for  the  sight  are 
lighted  up  to  a  sufficient  intensity  by  small  rheostats,  all  other  lamps 
having  each  a  key. 

All  electrical  conductors  for  the  motor  equipment,  for  the  lamps, 
and  for  the  firing  circuits  upon  the  carriage,  enter  the  counterweight 
well  through  a  duct  in  the  concrete,  the  opening  of  which  is  in  the  rear 


ARMAMENT 


227 


wall  of  the  well  a  short  distance  below  the  base  ring.  Thence  they 
hang  in  a  flexible  cable  or  bundle,  with  sufficient  slack  to  permit  trav- 
ersing through  the  allowed  angle,  and  enter  a  vertical  pipe  conduit 
near  the  center  of  rotation.  Thence  the  individual  conductors  are  led 
to  the  several  points  at  which  their  current  is  to  be  used. 

The  wiring  system  is,  as  far  as  possible,  inclosed  in  a  conduit  system 
of  wrought-iron  pipe,  fittings,  junction  boxes,  etc.,  all  with  interior 
insulation  and  outlet  insulators  at  the  ends  of  pipes.  The  lighting  and 
firing  wires  only  are,  at  points  where  armored  conduit  could  not  well 


.00 


.04 


.03 


.12 


.16 


.05 


.00 


be  used,  made  up  with  thimbles  hung  on  twisted  hooks,  and  so  carried 
to  their  destination. 

The  Buffer  Valve  (Fig.  18)  .—The  corrected  setting  of  the  buffer  valve 
is  determined  by  tripping  the  gun  several  times  and  varying  the  buffer 
valve  settings  until  a  satisfactory  counter-recoil  is  obtained.  Noting 
the  setting  of  the  buffer  valve,  then  obtain  from  the  chart  shown  in 
Figure  19  the  proper  setting  for  the  throttling  valve.  The  chart  shows 
curves  marked  buffer  and  throttling,  plotted  to  give  the  areas  of  orifice 
due  to  different  settings  of  these  two  valves. 


228  THE  SERVICE  OF  COAST  ARTILLERY 

Using  the  buffer-valve  setting  as  an  ordinate,  enter  the  chart  and 
obtain  the  amount  that  the  throttling  valve  should  be  closed  to  obtain 
the  proper  recoil  corresponding  to  this  buffer-valve  setting.  This 
amount  will  be  found  on  the  left-hand  vertical  scale  and  will  be  the 
horizontal  line  intersected  by  the  buffer-valve  setting-line  and  the 
buffer-valve  curve.  For  example,  suppose  that  the  emplacement  book 
records  show  at  last  target  practice  that  the  throttling  valve  set  at 
.16  gave  the  proper  recoil.  In  trial  after  the  attachment  of  the  buffer 
valve,  setting  the  same  at  30,  the  amount  of  change  in  the  setting  of 
the  throttling  valve  would  be  obtained  from  the  chart  by  following 
up  the  vertical  line  marked  30  until  it  intersected  the  buffer-valve 
curve,  then  following  the  horizontal  line  to  the  left  and  reading  its 
value  and  the  area  of  orifice  in  square  inches.  This  will  be  found  to  be 
approximately  .06  square  inch.  Subtracting  this  from  .16  gives  .10 
as  the  proper  setting  of  the  throttling  valve.  It  must  be  remembered 
that  any  change  in  the  opening  of  the  buffer  valve  necessitates  a  corre- 
sponding opposite  change  in  the  throttling  valve  unless  it  is  desired 
that  the  length  of  recoil  be  changed. 

MASKING    PARAPET   MOUNT 

In  this  type  of  carriage  the  gun  remains  above  the  parapet  for 
loading  and  firing,  but  can  be  lowered  below  the  level  of  the  crest 
of  the  emplacement  for  concealment.  The  15-Pounder  R.-F.  Gun, 
Driggs-Seabury,  is  mounted  usually  on  this  type  of  carriage  and  is 
shown  in  detail  in  Plate  XVI. 

The  principal  parts  of  the  mount  are  the  outer  base,  the  inner  base, 
the  counterweight,  the  counterweight  chains,  the  chain  wheels,  the 
operating  shaft,  the  pivot  socket  and  bar,  the  pivot  socket  clamping 
wedge,  the  pivot  yoke,  the  ball-bearing  washer,  the  horizontal  clamp, 
the  vertical  clamps,  the  oscillating  slide,  the  recoil  sleeve,  the  recoil 
cylinder  and  piston  rod,  the  shoulder  bar,  the  elevating  mechanism, 
the  sight  drum  and  gearing,  and  the  shield  and  braces. 

The  outer  base  is  set  into  a  concrete  foundation  and  forms  the 
ultimate  support  for  the  entire  mechanism.  It  is  cylindrical  in  shape, 
with  a  circular  hole  in  the  bottom  for  the  lower  part  of  the  inner  base1, 
and  two  flanges,  of  which  the  top  one  is  for  the  holding-down  bolts, 
while  the  other,  by  means  of  connecting  ribs,  supports  the  first.  The 
inner  top  edge  is  cut  away,  making  a  surface  inclined  15°  to  the  axis 
of  the  base  and  serving  to  help  center  the  inner  base. 

The  inner  base  is,  roughly,  a  cylinder  with  a  broad  flange  at  the 


ARMAMENT  229 

top.  At  the  lower  end  is  a  turned  surface  that  fits  into  the  hole  in  the 
bottom  of  the  outer  base,  and  3  inches  from  the  edge  of  the  flange  and 
on  the  under  side  is  a  surface,  inclined  15°  to  the  axis,  that  fits  into  the 
corresponding  surface  of  the  outer  base.  On  inner  surface  of  the  inner 
base  are  formed  two  vertical  ways  for  the  pivot-socket  bar  diametri- 
cally opposite  to  each  other,  and  at  the  top  of  these,  chain-wheel 
recesses  with  supports  and  holes  for  the  pin  and  the  shaft.  Near  the 
chain-wheel  recesses,  there  are  two  handholes  with  covers,  and  the  front 
edge  of  the  flange  carries  a  lug  for  the  operating  lever  and  the  ratchet- 
wheel  pawl.  The  interior  is  bored  to  receive  the  pivot  socket,  and  the 
upper  edge  has  two  holes  for  the  clamp  bolts.  The  two  bases  are  held 
together  by  eight  bolts. 

The  counterweight  is  a  cast-iron  ring  .weighted  with  lead.  It  is 
raised  and  lowered  between  the  two  bases,  and  it  has  two  grooves  to 
correspond  to  the  ways  of  the  inner  base,  and  two  shackle  plates  for 
attaching  the  chains. 

There  are  two  counterweight  chains;  they  pass  over  the  wheels 
and  are  attached  by  shackles  to  the  counterweight  and  by  eyebolts 
to  the  pivot-socket  bar. 

The  chain  wheels  are  assembled  to  the  inner  base,  one  by  a  pin  and 
the  other  by  the  operating  shaft;  the  first  is  bushed  with  bronze  and 
the  second  has  a  slot  for  a  spline  on  the  shaft.  The  wheels  have  sockets 
for  the  links  of  the  chain. 

The  operating  shaft  carries  the  right-hand  chain  wheel,  extends  to 
the  front  through  the  lug  on  the  inner  base,  and  is  squared  near  the  end 
for  the  ratchet.  The  ratchet  wheel  is  assembled  to  the  shaft  by  a 
taper  pin  and  the  lug  carries  the  ratchet-wheel  pawl. 

The  pivot  socket  is  cylindrical  in  shape  and  is  raised  and  lowered 
in  the  inner  base  by  a  bar,  to  which  the  chains  are  attached,  and  which 
passes  through  the  socket.  Two  bronze  collars  give  a  bearing  surface 
on  the  exterior,  while  the  interior  of  the  upper  part  is  bored  out  to 
give  two  bearing  surfaces  for  the  pivot  yoke.  A  \veb  forms  the  support 
for  the  ball-bearing  washer.  In  front  and  slightly  above  the  upper 
brass  collar  is  the  clamp  pad,  the  lower  surface  of  which  makes  a  slight 
angle  with  the  collar. 

The^  pivot-socket  clamping  wedge  is  shaped  to  the  socket  in  rear 
and  is  fastened  to  the  top  of  the  inner  base  by  two  screw  bolts  passing 
through  slots  in  the  clamp.  These  slots  are  at  the  ends  of  the  clamp, 
one  being  open,  while  the  other  is  closed.  Both  permit  motion  of  the 
clamp  to  right  or  left  without  wholly  removing  the  bolts.  On  the 
upper  portion  of  the  clamp,  next  the  socket,  there  is  an  inclined  surface 


230  THE  SERVICE  OF  COAST  ARTILLERY 

corresponding  to  that  of  the  clamp  pad  and  terminating  horizontally 
at  both  ends.  The  clamp  is  operated  by  means  of  a  lug. 

The  pivot  yoke  is  Y-shaped;  the  stem  seats  in  the  pivot  socket  and 
the  arms  furnish  the  trunnion  beds.  It  rests  on  the  ball-bearing  washer, 
and  those  that  are  made  of  steel  have  two  bronze  collars  for  the  bearing- 
surfaces.  Both  arms  have  threaded  seats  for  the  vertical  clamps  and 
lugs  on  the  inside  to  prevent  the  slide  from  springing  under  the  pressure 
of  the  clamps.  Four  lugs,  two  on  each  arm,  are  bored  out  for  the 
shield  braces,  and  the  seat  for  the  horizontal  clamp  is  cut  at  the  top  of 
the  front  part  of  the  stem.  The  cap  squares  are  secured  by  screw  bolts. 

The  ball-bearing  washer  is  seated  on  the  web  of  the  pivot  socket 
and  supports  the  pivot  yoke.  It  consists  of  a  row  of  hardened  steel 
balls,  inclosed  between  two  steel  washers  shaped  to  fit  them,  and  con- 
nected by  a  copper  thimble. 

The  horizontal  clamp  is  assembled  to  the  pivot  yoke,  and  consists 
of  a  lever  and  a  wedge.  The  lever  is  curved  and  has,  near  its  inner  end, 
a  projection  that  passes  through  the  wedge  and  is  assembled  to  the  pivot 
yoke  by  a  set  screw  or  a  filister  head  screw.  An  eccentric  cam  on  the 
projection  operates  the  wedge  and  retains  it  in  place  when  once  set 
home.  The  lower  part  of  the  wedge  is  shaped  to  the  interior  of  the 
pivot  socket. 

The  two  vertical  clamps  are  bent  handles  terminating  at  one  end 
in  a  screw  thread.  They  are  assembled  to  the  arms  of  the  pivot  yoke 
and  operate  by  friction  against  the  slide. 

The  oscillating  slide  is  a  casting,  made  of  bronze  in  the  mounts 
first  issued  and  of  steel  in  those  of  later  design.  The  bronze  slide 
consists  of  two  cheeks  connected  by  a  loop  and  web;  the  loop  is  under 
the  front  part  of  the  cheeks  and  the  web  is  across  the  front  of  the 
loop;  a  hole  for  the  piston  rod  is  bored  through  the  web.  On  the 
inside  of  each  cheek  there  are  two  guides  for  the  sleeve,  and  at  the  rear 
end  of  these  are  screwed  two  filling  pieces.  Near  the  front  there  are 
two  trunnions,  and  directly  under  these  two  lugs  giving  bearing  sur- 
faces for  the  vertical  clamps. 

Too  great  elevation  is  prevented  by  stops  at  the  rear  ends  of  these 
lugs.  The  left  trunnion  has  a  projecting  axis  for  the  shoulder  arm, 
an  elevating  rack  is  screwed  to  the  left  cheek  of  the  slide,  and  a  counter- 
recoil  buffer  of  leather  is  placed  on  the  inside  of  the  web.  In  the  steel 
slide  the  tops  of  the  cheeks  are  also  connected  by  a  strong  web  and  the 
loop  is  strengthened  by  two  diagonal  braces  extending  to  the  rear  ends 
of  the  cheek.  The  leather  buffer  is  omitted  in  the  steel  slide. 

Since  manufacture  the  bronze  oscillating  slides  have  been  strength- 


ARMAMENT  231 

ened  by  a  transom  bolted  across  the  top  and  two  diagonal  braces  bolted 
to  the  sides  to  and  the  loop  connecting  them. 

The  recoil  sleeve  screws  over  the  jacket  and  hoop  of  the  gun  and  is 
keyed  in  position;  it  is  shaped  to  fit  the  guides  of  the  slide,  and  has  a 
loop  with  a  beveled  surface  in  rear,  against  which  abuts  a  shoulder  on 
the  cylinder.  A  lug  in  front  stops  the  counter-recoil.  The  recoil 
sleeve  was  made  of  bronze  in  mounts  of  early  manufacture,  but  in  later 
mounts  they  are  of  steel,  with  the  guide  surfaces  faced  with  bronze. 

The  cylinder  has  a  smaller  diameter  in  front  than  in  rear,  the  two 
portions  being  joined  by  an  inclined  curved  surface.  On  the  interior 
the  smaller  part  is  cylindrical  and  is  intended  as  a  seat  for  the  spring. 

The  travel  of  the  piston  is  limited  to  the  larger  part  of  the  cylinder. 
Constant  resistance  is  obtained  by  the  passage  of  the  liquid  from  one 
side  of  the  piston  to  the  other  through  varying  orifices,  depending  upon 
the  varying  diameters  of  the  interior.  These  diameters  vary  with  the 
position  of  the  piston  in  such  a  way  as  to  obtain  the  desired  resistance. 
The  piston  rod  and  head  form  one  piece,  the  latter  being  of  the  same 
diameter  as  the  front  of  the  larger  portion  of  the  cylinder.  Springs  of 
a  circular  or  rectangular  cross-section  abut  against  the  piston  head  and 
the  front  end  of  the  cylinder.  There  is  a  cylinder  head  in  the  rear,  and 
stuffing-box  glands  front  and  rear.  The  forward  end  of  the  piston  rod 
is  threaded  for  two  nuts.  A  vent  and  filling  hole  are  placed  in  the  side 
of  the  cylinder. 

The  shoulder  bar  is  pivoted  to  the  left  trunnion,  kept  in  position 
by  a  washer  and  screw  bolt  in  the  trunnion,  the  shoulder-bar  guide  is 
elevated  and  depressed  by  a  worm  and  rack;  the  bar  is  shaped  to  give 
a  grip  for  the  hand  and  carries  the  indicator  for  the  elevation  scale, 
the  complete  sight  drum,  the  sight,  the  elevating  handwheel  and  worm, 
and  the  shoulder  piece. 

The  elevating  mechanism  consists  of  a  rack,  screwed  to  the  oscillating 
slide,  and  a  worm,  spring,  ball-bearing  washer,  and  handwheel  assembled 
on  a  vertical  shaft  to  lugs  on  the  shoulder-bar. 

The  sight  drum  and  gearing  consists  of  an  indicator  drum,  with  a 
guard,  a  cover,  a  coil  spring,  a  clamp  bolt  and  nut,  and  a  rack.  The 
cover  fits  inside  the  drum  inclosing  the  spring,  the  cover  and  drum 
being  screwed  together.  The  spring  has  one  end  secured  to  the  drum 
and  the  other  to  a  bolt  which  is  screwed  into  the  shoulder-bar.  An 
axis  and  pinion  projects  from  the  indicator  drum,  the  former  being 
seated  in  the  shoulder  bar  and  the  latter  engaging  the  rack  on  the 
shoulder-bar  guide.  The  indicator  drum  has,  on  the  outer  cylindrical 
surface,  a  German  silver  strip  on  which  the  ranges  are  marked.  The 


232  THE  SERVICE  OF  COAST  ARTILLERY 

whole  is  assembled  to  the  shoulder  bar  by  the  clamp  bolt  and  nut. 
The  guard  is  screwed  to  the  shoulder  bar  and  has  a  rectangular  cut 
that  permits  a  view  of  the  graduated  strip;  there  is  a  small  pointer 
at  one  side  of  this  opening  for  indicating  ranges. 

The  shield  is  a  plate  so  bent  that  the  two  parts  make  an  angle  of 
135°  with  each  other.  The  gun  and  the  line  of  sight  pass  through 
apertures,  and  there  are  holes  for  the  bolts  used  to  assemble  the  shield 
to  the  braces;  these  latter  are  four  in  number  and  are  supported  in 
lugs  on  the  pivot  yoke. 

The  lanyard  is  a  cord  wound  with  brass  wire  and  passing  through 
three  guides;  one  on  the  breech  of  the  gun,  another  on  the  sleeve, 
and  the  third  on  the  left  cheek  of  the  slide.  There  is  a  handle  on  one 
end  and  a  button  on  the  other,  while  a  small  check  nut,  held  in  place 
by  a  set  screw,  prevents  too  much  slack  near  the  breech. 


THE    DRIGGS-SEABURY    6-POUNDER   PARAPET    MOUNTS 

(See  Fig.  16) 

The  later  mounts  supplied  by  this  company  differ  in  several  details 
from  the  earlier  ones.  Though  all  are  designated  on  the  name  plate  as 
model  1898,  those  of  later  manufacture  are  described  herein  as  model 
1898  modified. 

The  principal  parts  of  the  model  1898  mount  are  the  axle,  the  wheels, 
the  pivot  socket,  and  ball-bearing  washer,  the  trail  flasks,  the  trail 
piece,  the  spade,  the  trail  wheel  and  cradle,  the  trail-traverse  roller, 
the  pivot  yoke,  the  horizontal  and  vertical  clamps,  the  recoil  sleeve, 
the  recoil  cylinder  and  piston  rod,  the  counter-recoil  spring,  the 
shoulder  bar,  the  shield  and  braces,  the  anchorage  and  the  ammunition 
boxes. 

The  axle  is  a  square  bar  of  forged  steel,  terminating  at  each  end 
in  an  arm  for  the  hub  of  the  wheel  and  bent  to  the  front  in  the  center 
to  make  room  for  the  pivot  socket.  The  wheels,  washers,  linchpins 
and  fasteners  are  similar  to  those  on  field  carriages  for  3.2-inch  guns. 

The  pivot  socket  is  a  steel  casting,  rectangular  in  shape;  the  two 
sides  being  extended  front  and  rear  beyond  the  ends  to  form  four 
flanges  to  which  are  riveted  the  trail  flasks.  In  front,  at  the  bottom, 
a  horizontal  flange  is  similarly  formed  and  rests  upon  the  curved  part 
of  the  axle.  The  interior  is  bored  to  form  two  cylindrical  bearing 
surfaces  for  the  pivot  yoke,  one  at  the  top  and  the  other  near  the  bot- 
tom, the  space  between  being  cored  out  to  prevent  contact  with  the  yoke. 


ARMAMENT  233 

In  the  bottom  of  the  socket  a  hole  is  drilled  for  the  pivot  bolt,  and  a 
shallow  circular  groove  formed  with  four  small  drainage  holes. 

A  seat  for  the  horizontal  clamp  is  formed  by  drilling  and  partly 
threading  a  hole  through  the  right  side,  and  two  stops  are  placed  on 
top  in  rear  to  limit  the  rotation  of  the  pivot  yoke.  A  ball-bearing 
washer,  consisting  of  a  row  of  hardened  steel  balls,  held  between  two 
steel  washers  by  means  of  a  copper  thimble,  rests  on  the  bottom  of  the 
pivot-socket  cavity  and  supports  the  weight  of  the  pivot  yoke  and 
assembled  parts. 

The  two  steel  trail  flasks  are  riveted  to  the  flanges  of  the  pivot 
socket  and  the  axle  brackets  in  front  and  to  two  transoms  and  the 
trail  piece  in  rear.  The  construction  is  further  stiffened  by  riveting 
steel  angles  to  the  inside  lower  edges  of  the  flasks  which  also  serve  as 
supports  for  the  trail-wheel  bearings  and  for  the  bottom  of  the  trail 
toolbox.  This  toolbox  is  a  compartment  formed  between  the  trail 
flasks  by  the  two  transoms,  and  closed  by  a  hinged  lid  on  top.  A 
step,  a  handle,  and  the  fastenings  for  the  handspike  are  riveted  to  the 
outside  of  the  right  flask,  and  a  step,  a  handle,  and  the  fastenings  for 
the  sponge  rod  to  the  left,  flask. 

The  trail  piece  is  a  bronze  casting  which  contains  the  lunette  and 
seats  for  the  handspike,  spade  pin,  the  trail-wheel  cradle  pin,  and  the 
traverse  roller.  The  spade  is  hinged  to  lugs  on  the  upper  side  of  the 
trail  piece  by  a  pin,  and  by  this  arrangement  can  either  be  placed  in 
position  for  use  or  rotated  over  the  end  of  the  trail  and  laid  upon  the 
latter  out  of  the  way. 

The  trail-wheel  cradle  carries  the  trail  wheel  at  one  end  and  is 
pivoted  to  the  trail  piece  at  the  other.  The  cradle  may  be  secured  in 
either  of  two  positions  by  means  of  a  pin,  which  passes  through  the 
hollow  axle  of  the  wheel.  In  the  lower  position  this  pin  is  inserted 
through  bearings  on  the  under  side  of  the  trail  and  in  the  upper  the  pin 
is  passed  through  the  flasks.  When  secured  in  the  lower  position  the 
wheel  supports  the  trail,  while  in  the  upper  it  is  raised  between  the 
flasks  and  the  trail  rests  on  the  ground. 

The  traverse  roller  is  ellipsoidal  in  shape  and  is  assembled  to  the 
trail  piece  beneath  with  the  axis  at  right  angles  to  that  of  the  trail 
wheel.  Its  function  is  to  permit  easy  movement  of  the  trail  in  aiming. 

The  pivot  yoke  is  Y-shaped,  the  stem  seating  on  the  ball-bearing 
washer  in  the  pivot  socket  and  the  arms  forming  the  trunnion  beds. 
Two  bearing  surfaces  are  turned  on  the  stem  to  fit  those  in  the  socket, 
and  its  base  is  drilled  and  tapped  for  the  pivot  bolt. 

The  upper  bearing  is  slotted  for  the  horizontal  clamp  and  the  right 


234  THE  SERVICE  OF  COAST  ARTILLERY 

arm  is  drilled  for  the  vertical  clamp.  On  each  arm  there  are  two  lugs 
through  which  the  shield  braces  pass.  The  cap  squares  are  secured  by 
screw  bolts. 

The  horizontal  clamp  consists  of  a  screw  bolt,  the  outer  end  of  which 
is  bent  to  form  a  lever  handle,  a  pad,  and  a  button.  On  the  inner  side 
the  pad  is  knurled  and  shaped  to  the  pivot  yoke,  while  on  the  outer 
side  it  has  an  undercut  groove,  open  at  the  top,  in  which  the  button 
is  held.  Rotation  of  the  pad  is  prevented  by  a  stud  on  the  lower  edge. 

The  oscillating  slide  is  a  bronze  casting  consisting  of  two  cheeks 
connected  at  their  lower  edges  by  a  web.  On  the  outside  of  each 
cheek  there  is  a  trunnion  and  on  the  inside  two  guides  in  which  the 
sleeve  works;  the  right-hand  cheek  also  has  seats  for  the  shoulder  bar 
and  the  vertical  clamp  bolt.  A  hole  for  the  piston  rod  is  drilled  through 
the  front  of  the  web,  and  a  filling  piece  is  screwed  on  the  rear  end  of 
each  cheek  between  the  guides  to  prevent  the  sleeve  and  gun  running 
out  of  the  slide  in  the  operation  of  mounting,  or  whenever  the  piston 
rod  is  disconnected  from  the  slide. 

The  vertical  clamp  consists  of  a  screw  bolt  and  a  lever  handle, 
the  latter  provided  with  a  lug  at  one  end  and  threaded  for  the  bolt. 
A  circular  slot  is  cut  in  a  flange  on  the  right  side  of  the  oscillating  slide 
to  form  a  seat  for  the  head  of  the  bolt.  The  circular  head  of  this  bolt 
is  cut  away  on  the  inside  top  and  bottom  to  the  width  of  the  radius 
of  the  slot  in  the  slide.  The  lug  thus  formed  works  in  the  slot  and 
prevents  turning  of  the  bolt,  while  the  remaining  circular  portion  of 
the  head  is  in  contact  with  the  inner  side  of  the  flange  of  the  slide, 
and  serves  to  clamp  the  latter  when  the  bolt  is  drawn  in  by  screwing 
on  the  handle. 

The  recoil  sleeve,  which  is  also  a  bronze  casting,  screws  over  the 
jacket  and  hoop  of  the  gun  and  is  keyed  in  position.  It  has  bearings 
on  each  side  formed  to  fit  those  of  the  slide  and  a  heavy  loop  beneath 
bored  out  for  the  insertion  of  the  recoil  cylinder  and  shaped  to  fit 
against  a  shoulder  on  the  latter.  An  eye  in  a  lug  on  top  affords  a  con- 
venient attachment  for  handling  the  gun  in  mounting  and  dismount- 
ing. 

The  recoil  cylinder  is  of  bronze  and  is  closed  by  a  stuffingbox  in 
front  and  a  head  and  stuffingbox  in  rear.  At  about  the  center  a  cir- 
cumferential rib  or  shoulder  is  formed  on  the  exterior,  which  abuts 
against  the  loop  on  the  sleeve.  The  interior  of  this  front  portion  of  the 
cylinder  is  bored  cylindrically  and  merely  affords  the  additional  length 
required  for  the  counter-recoil  spring  over  that  needed  for  the  move- 
ment of  the  piston  in  recoil.  The  part  of  the  cylinder  in  rear  of  the 


ARMAMENT  235 

exterior  shoulder  is  that  in  which  the  piston  head  works  and  is  bored 
larger. 

The  piston  and  all  cross-sections  of  the  cylinder  are  circular;  the 
oil,  therefore,  always  has  an  annular  opening  to  pass  through  while 
being  forced  from  one  side  of  the  piston  to  the  other  as  the  cylinder 
and  piston  move  relatively  to  each  other.  This  opening  is  the  annular 
clearance  to  the  piston  (and  is  equal  to  the  area  of  cross-section  of  the 
cylinder  minus  the  area  of  cross-section  of  the  piston).  This  opening 
is  varied  by  giving  the  cylinder  a  different  area  of  cross-section  at  each 
point  of  recoil.  The  greatest  area  of  cross-section  of  the  cylinder  is  at 
the  point  at  which  the  velocity  of  retarded  recoil  is  the  greatest.  The 
areas  are  so  varied  relative  to  the  velocity  of  retarded  recoil  that  the 
resistance  to  recoil  (that  is,  the  pull  on  the  piston  rod)  is  nearly  con- 
stant. 

These  mounts  were  designed  to  use  a  mixture  of  glycerin  and  water 
in  the  cylinders,  and  the  earlier  mounts  as  issued  wrere  supplied  with 
this  mixture.  No  issues  of  glycerin  are  made,  however,  as  the  Ordnance 
Department  has  found  a  neutral  oil  to  be  superior.  This  oil,  called 
"hydroline,"  is  now  issued  and  used  in  these  as  well  as  all  other  hy- 
draulic recoil  cylinders. 

Through  the  side  of  the  cylinder  near  the  rear  end,  a  filling  hole  is 
drilled,  closed  with  a  small  screw  plug. 

The  piston  head  and  rod  are  formed  from  one  piece  of  steel.  The 
rod  extends  on  both  sides  of  the  head,  the  portion  in  front,  which  is 
longer  and  larger  in  diameter,  ending  in  an  eye  and  being  threaded  for 
the  piston-rod  nuts,  while  the  part  in  rear  of  the  head  projects  through 
the  rear  stuffingbox  and  serves  as  a  support  and  guide  for  the  head 
during  recoil.  The  counter-recoil  spring  is  a  coiled  spring  strung  upon 
the  rod  in  front  of  the  head  and  abutting  against  the  head  and  the  front 
end  of  the  cylinder. 

The  shoulder  bar  is  a  straight  bronze  arm  the  forward  end  of  which 
is  shaped  to  slide  into  an  undercut  seat  on  the  oscillating  slide.  A  leaf 
spring  on  the  bar  locks  it  in  its  seat.  The  rear  end  of  the  bar  is  fitted 
with  a  wooden  shoulderpiece  suitably  padded  with  a  piece  of  rubber 
hose.  A  bronze  handle  and  a  guide  or  deflector  to  prevent  the  ejected 
cases  from  hitting  the  gunner  are  attached  to  the  left  side  of  the  shoulder- 
piece. 

The  shield  consists  of  a  steel  plate  about  J  inch  thick,  which  is  at- 
tached to  the  carriage  by  the  four  shield  braces  passing  through  lugs  on 
the  pivot  yoke.  The  upper  part  of  the  shield  is  bent  to  the  rear, 
forming  an  angle  of  135  degrees  with  the  lower  vertical  part,  and  suitable 


236  THE  SERVICE  OF  COAST  ARTILLERY 

apertures  are  cut  out  for  the  gun,  the  line  of  slide,  and  bolts  of  the 
braces. 

The  anchorage  consists  of  one  V-rod,  two  anchor  bolts  and  nuts, 
two  anchor  plates,  and  one  axle  brace  and  anchor  stirrup. 

The  brace  and  stirrup  is  a  steel  plate,  assembled  to  and  under  the 
ammunition  and  axle  brackets.  The  stirrup  is  directly  beneath  the 
pivot  socket,  is  braced  and  reenforced  from  the  rear,  and  has  a  hole 
for  the  hook  of  the  V-rod.  The  angle  end  of  the  V-rod  terminates  in  a 
hook  through  which  a  pinhole  is  drilled.  The  two  ends  of  the  rod  are 
permanently  connected  to  the  anchor  bolts  by  eyes,  and  the  anchor 
plates  are  assembled  on  the  bolts  by  nuts. 

Two  ammunition  boxes,  each  holding  nine  rounds,  are  carried  on 
brackets  on  the  axle,  on  either  side  of  the  pivot  socket.  These  boxes 
are  rectangular  in  shape  and,  except  the  door,  which  is  of  steel,  are 
made  of  malleable-iron  sheets.  The  interior  is  fitted  with  three  tran- 
soms or  partitions,  two  of  malleable  iron  and  one  of  wood,  provided 
with  holes  for  receiving  the  ammunition.  The  door  is  lined  on  the 
inside  with  felt,  is  hinged  at  the  bottom,  has  two  steel  hangers  to  support 
it  when  open,  and  is  closed  by  a  hasp.  Two  handles  are  riveted  on  each 
box,  and  two  trunnion  bars,  one  front  and  one  rear,  pass  through  near 
the  bottom  and  project  slightly  on  either  side. 

The  brackets  which  support  these  boxes  fit  over  the  axle,  are  bolted 
to  the  brace,  and  each  has  two  undercut  lugs  in  the  front,  into  which 
the  trunnion  bars  of  the  boxes  slip,  and  two  slotted  lugs  in  rear.  The 
rear  lugs  are  drilled  and  tapped  for  the  screw  bolts,  which  serve  as  pivots 
for  the  box  holders.  These  holders  are  clips,  fitted  with  springs  to 
retain  them  in  place,  which  swing  over  the  rear  trunnion  bars  of  the 
ammunition  boxes  and  secure  them  in  place. 

MORTAR   CARRIAGES 

The  method  of  mounting  mortars  is  such  as  to  require  the  classifi- 
cation of  their  carriages  under  a  special  head.  A  strict  interpretation 
of  the  definitions  of  the  other  classes  readily  shows  that  they  are  neither 
barbette,  disappearing,  masking  parapet,  or  casemate,  but  rather  a 
combination  of  the  two  principal  classes.  The  12-inch  B.-L.  mortar 
mounted  on  spring  return  carriage  is  shown  in  Plate  IV  and  Fig.  11. 

The  carriage  is  designed  to  deliver  all-around  high-angle  fire,  of 
from  45  to  65  degrees  elevation.  It  is  prevented  from  creeping  after 
set  in  azimuth  by  a  traversing  brake  which  must  be  released  before 
pointing  the  piece  in  azimuth. 


ARMAMENT  237 

With  the  800-pound  projectile  and  full  charge,  the  recoil  is  approxi- 
mately 19  inches,  measured  on  the  piston-rods. 

The  horizontal  piece,  when  fully  counter-recoiled,  is  54  inches  above 
the  loading  platform,  and  the  projectile,  in  loading,  is  wheeled  directly 
into  the  breech  recess,  the  tray  of  the  ammunition  trucks  forming  the 
loading  trays. 

It  is  arranged  for  either  lanyard  or  electric  firing,  and  in  the  latter 
case  the  pieces  may  be  fired  independently  or  the  entire  four  in  a  pit 
at  once,  from  the  outlet  box,  or  the  battery  commander  from  his  station 
may  fire  either  by  pit  or  by  battery. 

After  loading,  the  piece  must  be  again  elevated  to  43  degrees  before 
the  electric  connection  for  firing  is  automatically  made. 

In  lanyard  fire,  the  lanyard  is  hooked  into  the  stopper  of  the  lanyard 
attachment  in  the  floor  plate,  the  attachment  lanyard  giving  a  direct 
pull  on  the  primer. 

Action  of  Carriage. — Upon  firing,  the  piece  and  top  carriage  rotate 
to  the  rear  and  downward  about  the  fulcrum  shaft,  compressing  the 
counter-recoil  springs  and  forcing  the  crossheads  and  piston  downward 
until  the  resistance  in  the  recoil  cylinders  stops  the  motion,  after  which 
the  compressed  counter-recoil  springs  immediately  return  the  piece  to 
the  loading  and  firing  height.  The  movement  of  the  crank  pins  through 
the  arc  of  a  circle  causes  the  recoil  cylinders  and  guides  to  oscillate 
about  their  trunnions. 

Principal  Parts. — The  carriage  consists  of  the  following  principal 
parts,  viz.:  Base  ring  and  floor  plates,  traversing  roller  system,  racer, 
top  carriage  or  saddle,  recoil  system,  counter-recoil  springs  and  buffer 
stops,  elevating  system,  traversing  system,  azimuth  circle  and  pointer, 
elevation  quadrant,  lanyard  attachment,  electrical  attachments,  and 
shot  trucks  and  tongs. 

Base  Ring. — The  base  ring  is  of  cast  iron  in  one  piece,  and  is  secured 
in  its  position  by  twenty-four  1.75-inch  anchor  bolts.  The  outer  flange 
of  the  base  ring,  14  feet  in  diameter,  which  contains  the  bolt  holes,  rests 
upon  the  upper  step  of  the  well,  whose  surface  is  24.5  inches  below  the 
floor  level  of  the  emplacement. 

The  top  surface  is  turned,  forming  the  lower  roller  path  and  a 
vertical  annular  flange  forms  the  male  part  of  the  pintle.  The  traversing 
rack  is  attached  on  the  inside  below  the  roller  path. 

Eight  brackets,  rigidly  supporting  the  azimuth  circle  castings,  are 
bolted  to  the  outer  flange,  these  brackets  and  castings,  together  with 
the  radial  angle  irons  whose  outer  ends  are  embedded  in  the  concrete, 
furnishing  the  support  for  the  circle  of  cast  iron  removable  floor 


238 


THE  SERVICE  OF  .COAST  ARTILLERY 


plates.  There  are  sixteen  plates,  retained  in  position  by  countersunk 
screws. 

Traversing  Roller  System. — The  racer  rests  and  is  traversed  upon 
a  circle  of  twenty-four  live,  conical,  traversing  rollers  of  forged  steel, 
with  a  single  flange.  The  rollers  are  7.5  inches  in  maximum  diameter, 
and  their  axes  are  held  in  the  radial  position  by  a  cast-steel  distance 
ring  in  six  sections,  in  which  their  bronze-bushed  journals  have  bearings. 
The  distance  ring  has  oil  grooves  finished  around  its  top  edges,  reaching 
through  oil  tubes  in  the  racer. 

Racer. — The  racer  is  of  cast  iron  in  one  piece,  13  feet  9.5  inches  in 
diameter.  Its  lower  surface  is  turned,  forming  the  upper  roller  path, 
corresponding  to  the  lower  roller  path  on  the  base  ring.  The  outside 
annular  flange  extends  downward,  fitting  over  the  pintle  with  0. 063-inch 
diametral  clearance.  It  is  of  cellular  structure,  and  upon  its  front  edge 
are  cast  two  lugs  or  brackets,  to  which  the  top  carriage  or  saddle  is 


GENERAL  METHOD  OF  CONTROLLING  THE  ENERGY 
OF  RECOIL  IN  MORTAR   CARRIAGES. 

FlG.   20. 

pivoted  by  means  of  a  forged  steel  fulcrum  shaft.  On  each  side  of  the 
longitudinal  openings  are  openings  and  supporting  bearings  for  the 
recoil  cylinders.  The  reenforce  piec'es,  one  on  either  side  of  the  opening, 
have  been  added  to  the  original  racers  to  give  additional  strength  at 
these  points.  Three  removable  oil  plugs  permit  oiling  the  pintle  and 
trave  sing  rollers. 

Top  Carriage. — The  top  carriage  or  saddle,  of  cast  iron,  consists 
of  two  arms  connected  by  a  heavy  web.  The  upper  ends  of  these  arms 
form  the  trunnion  beds  in  which  the  mortar  is  mounted  and  carry  the 
crank  pins  which  operate  the  recoil  brake.  The  saddle  is  inclined  to  the 
rear  at  an  angle  of  about  41  degrees,  the  lower  ends  being  held  by  the 
fulcrum  shaft.  Between  the  fulcrum  and  the  trunnions  are  placed 
openings  for  the  spring  guide  rods  and  the  seat  for  the  cap  of  the  rock- 
ing counter-recoil  springs. 

Recoil   System. — Fig.  20    shows   the  general  arrangement  of  the 


ARMAMENT  239 

hydraulic  brake  and  its  connections  in  its  essential  principles  and  in 
relative  positions  of  parts  for  mortar  carriages  "in  battery." 

The  recoil  is  checked  by  two  hydraulic  cylinders  with  return  pas- 
sages. These  cylinders  are  provided  with  trunnions  and  oscillate  in 
brackets  bolted  to  the  top  of  the  racer  on  each  side  of  its  central  opening, 
their  lower  ends  extending  some  distance  below  the  racer. 

They  are  of  cast-steel,  7.75  inches  interior  diameter  arid  are  fitted 
with  3.5-inch  forged-steel  piston  rods  working  through  stuffing-boxes 
at  both  ends  of  the  cylinders.  Each  stuffingbox  contains  six  rings  of 
0.625-inch-square  Garlock  water-proof  hydraulic  packing. 

About  the  middle  of  the  rod  a  piston  is  formed  out  of  the  solid,  on 
which  is  formed  a  bronze  bushing.  The  connecting  or  return  passages 
are  formed  along  one  side  between  the  ends  of  each  cylinder,  entering 
the  upper  end  immediately  above  the  head,  and  five  holes  0.7-inch  in 
diameter  are  bored  at  proper  intervals,  connecting  the  passages  with  the 
cylinders.  The  energy  of  recoil  is  taken  up  by  the  resistance  which  the 
fluid  offers  to  being  driven  through  these  holes,  which  are  successively 
closed  by  passage  of  the  piston  over  them.  Plugs  are  provided  for 
closing  or  partly  closing  the  holes.  The  upper  face  of  each  piston 
has  an  annular  recess,  which,  at  the  end  of  the  counter  recoil,  passes 
over  the  annular  projection  or  buffer  on  the  upper,  bronze,  cylinder  head. 
The  fluid  thus  imprisoned  being  able  to  escape  by  the  clearance  only, 
its  resistance  gradually  checks  the  movement  and  consequently  the 
mortar  returns  gently  to  the  firing  position. 

Each  cylinder  has  one  filling  hole,  on  its  rear  side,  near  its  upper  end. 

For  all  charges  the  cylinders  should  be  filled  to  the  level  of  the  filling- 
holes,  removing  for  this  purpose  both  plugs,  so  as  to  permit  the  air  to 
escape. 

A  neutral  oil  of  specific  gravity  of  about  0.85  (such  as  the  hydroline 
at  present  issued),  is  used,  and  with  this  oil  the  working  pressure  in 
the  cylinders  is  about  4,000  pounds  per  square  inch  and  the  piston-rod 
compression  about  150,000  pounds.  A  denser  oil  would  cause  a  higher 
pressure  in  the  cylinders  and  therefore  shorten  the  recoil  slightly. 

To  give  the  proper  recoil  the  throttling  plugs  should  be  arranged  in 
each  cylinder,  from  top  to  bottom,  as  follows:  First  hole  closed;  second 
hole  half  open;  third  hole  quarter  open;  fourth  and  fifth  holes  open. 

To  facilitate  inspections,  the  tops  of  the  throttling  plugs  have  been 
stamped  with  a  "C,"  "£,"  "J,"  and  "0"  to  indicate  whether  the  holes 
are  closed,  half  open,  quarter  open,  or  open. 

The  recoil  system  is  at  present  undergoing  certain  changes  which 
when  completed  will  result  in  the  return  passageway  being  entirely 


240  THE  SERVICE  OF  COAST  ARTILLERY 

closed.  In  place  of  this  passageway  three  channels  about  2|  inches 
wide  and  varying  in  depth  from  .02  to  .087  inch  have  been  cut  the 
length  of  the  recoil  cylinder. 

If  it  is  desired  to  measure  the  recoil,  it  can  be  done  on  one  of  the 
piston  rods  by  making  several  turns  around  it  with  fine  twine  and  ty ing- 
it  tightly  just  where  the  piston  rod  enters  the  stuffingbox.  The 
height  of  the  twine  above  the  stuffingbox,  after  firing,  will  indicate  the 
counter  recoil,  which  will  also  be  the  recoil  if  the  mortar  has  returned 
to  the  firing  position.  If  it  does  not  return  to  the  firing  position  the 
springs  should  be  compressed  as  hereafter  described. 

The  lower  ends  of  the  hydraulic  cylinders  are  connected  by  an 
equalizing  pipe,  in  which  is  made  an  emptying  coupling,  so  that  the 
resistance  and  the  pressure  in  both  cylinders  shall  be  equal.  The 
coupling  is  provided  for  emptying  the  cylinders  at  a  convenient  po.int. 

Bronze  plugs  are  provided  which  can  be  used  to  replace  the  equaliz- 
ing pipes  thus  continuing  the  piece  in  action  after  their  injury.  On 
the  top  of  each  cylinder  are  bolted  two  guides  of  cast  steel,  between 
which  moves  a  sliding  crosshead,  into  which  the  upper  end  of  the 
piston-rod  is  secured  by  means  of  a  collar  and  nut.  The  crossheads  are 
assembled  over  the  crank  pins,  of  forged  steel,  which  are  forced  into 
the  saddle,  just  below  the  trunnion  beds,  by  hydraulic  pressure  and 
riveted. 

Counter-Recoil  Springs  and  Buffer  Stops. — The  saddle  is  sup- 
ported at  a  point  about  one-third  of  its  length  from  the  fulcrum  shaft 
by  five  columns  of  springs.  Each  column  consists  of  five  double-coil 
helical  springs,  threaded  on  a  rod  of  forged  steel.  These  five  rods, 
arranged  in  a  row  side  by  side,  are  used  to  give  the  necessary  initial 
compression  to  the  springs  in  assembling  the  carriage,  and  afterwards 
serve  simply  to  guide  the  springs  laterally. 

The  lower  ends  of  these  spring  columns  rest  in  a  springbox,  of  cast- 
iron,  and  the  upper  ends  bear  against  a  spring  cap. 

The  springbox  is  hung,  by  means  of  trunnions,  in  two  brackets,  of 
cast  iron,  bolted  to  the  upper  surface  of  the  racer,  which  permit  it  to 
oscillate  during  recoil  to  the  different  inclinations  of  the  spring  columns. 
The  spring  cap,  performing  essentially  the  same  office  above  as  the 
springbox  does  below,  is  a  thin  rectangular  steel  casting  fitting  over 
the  top  of  the  spring  columns,  and  having  upon  its  upper  surface  a 
well-rounded  knife-edge  bearing.  During  recoil  this  bearing  rocks  in  a 
groove  running  across  the  lower  surface  of  the  saddle  web.  Both  the 
spring  cap  and  box  are  perforated  to  allow  the  ends  of  the  spring  rods 
to  pass  freely  through  them. 


ARMAMENT  241 

As  an  additional  precaution  against  shock  when  returning  to  the 
firing  position,  buffer  stops  are  provided.  These  are  made  up  of 
alternate  layers  of  balata  and  steel  plates,  and  are  held  between  the 
guides  under  the  caps.  The  cross  heads  moving  between  the  guides 
during  counter-recoil  strike  these  buffers  when  the  mortar  returns  to 
the  firing  position,  and  are  maintained  in  pressure  contact  under  the 
guide  caps  by  the  counter-recoil  springs. 

Elevating  System. — A  circular  rack  of  cast  steel  is  bolted  longi- 
tudinally to  the  mortar  on  the  under  side,  so  that  the  center  from  which 
its  pitch  line  is  struck  is  at  the  intersection  of  the  axis  of  the  trunnion 
and  bore.  This  rack  engages  in  a  pinion  of  forged  steel  mounted  on  a 
heavy  shaft  on  the  under  surface  of  the  saddle  web,  to  which  motion 
is  given  by  gears  connecting  with  a  second  shaft  extending  across  the 
upper  face  of  the  saddle  web  and  bearing  a  hand  wheel  at  each  end. 
The  saddle  web  is  cored  out  to  permit  the  passage  of  the  rack  in  ele- 
vating. 

The  mortar  is  held  in  the  loading  and  firing  positions  by  means  of 
a  hand  nut  on  the  handwheel  shaft,  which  locks  that  shaft  by  pressing 
the  steel  handwheel  pinion  against  an  adjoining  bushing,  which  together 
form  a  conical  friction  clutch.  To  protect  the  teeth  on  the  elevating 
gearing  from  injury,  which  may  be  caused  by  the  inertia  effects  of  the 
handwheel  during  the  change  of  elevation  in  recoil,  the  elevating  shaft 
has  keyed  to  it  a  friction  cone.  This  cone  fits  into  the  bronze  elevating 
gear,  which  is  loose  on  its  shaft  and  engages  the  steel  pinion  on  the 
handwheel  siiaft.  By  means  of  a  washer  and  nut  the  bronze  elevating 
gear  may  be  forced  onto  the  friction  cone  with  any  desired  pressure, 
i.  e.,  with  sufficient  pressure  to  prevent  slipping  during  elevating  or 
depressing  or  an  undue  amount  of  slipping  during  the  recoil.  The 
friction  between  cone  and  gear  will  be  sufficient  if  the  united  effort  of 
two  men  applied  to  the  handwheels  is  required  to  cause  a  slipping  when 
an  attempt  is  made  to  depress  below  the  minimum. 

An  elevation  lock  is  to  be  applied  to  lock  the  mortar  in  the  hori- 
zontal position  against  the  elevating  stop  while  loading.  It  consists 
of  a  latch  bolt  with  a  lever  for  withdrawing  it,  arranged  on  the  top  of 
the  carriage,  engaging  with  a  strike  on  the  elevating  rack.  It  is  operated 
by  the  cannoneer  at  the  right  elevating  handwheel. 

Traversing  System. — The  circular  traversing  rack  on  the  inside  of 
the  base  ring  has  meshing  with  it  a  pinion  on  a  vertical  shaft  which 
passes  down  through  the  racer  and  having  at  its  upper  end  a  worm- 
wheel.  Motion  is  given  the  latter  by  means  of  two  cranks  mounted 
on  a  worm  shaft.  The  worm  shaft,  worm  wheel,  and  the  part  of  the 


242  THE  SERVICE  OF  COAST  ARTILLERY 

vertical  shaft  above  the  racer  are  incased  in  a  cast-iron  standard,  which 
has  oil  and  drain  holes  conveniently  placed  and  also  so  arranged  that 
the  worm  and  the  gear  rim  run  in  oil. 

In  order  to  maintain  the  piece  without  further  movement  until  fired, 
after  having  been  set  in  azimuth,  it  is  expected  that  a  traversing  brake 
will  be  applied. 

It  has  been  arranged  with  a  pedal  in  the  rear  of  the  cast-iron 
standard  which  carries  the  gearing  and  so  as  to  be  maintained  "on" 
by  a  coil  spring  acting  to  set  the  brake  levers  to  grip  the  top  and 
bottom  surfaces  of  the  traversing  rack,  thus  retaining  the  carriage  in 
a  fixed  position.  When  about  to  traverse,  the  cannoneer  at  the 'crank 
places  a  foot  on  the  pedal,  compressing  the  spring  and  permitting  free 
movement. 

Azimuth  Circle  and  Pointer. — A  brass  circular  strip  in  eight  sections 
about  1  inch  wide  graduated  to  degrees,  is  attached  to  the  top  side 
of  the  azimuth-circle  castings  which  surround  the  racer.  Attached  to 
the  racer  is  a  small  brass  pointer  or  subscale.  This  pointer  is  sub- 
divided to  0.05  of  a  degree  and  stamped  in  hundredths  of  a  degree. 
After  final  adjustment  it  is  dowel-pinned  to  the  racer. 

An  improved  azimuth  pointer  has  been  tested.  It  has  a  deflec- 
tion scale  for  wind  and  moving  targets  to  be  used  in  combination  with 
deflection  scales  for  the  drift  of  the  different  projectiles  used  with  the 
piece.  Adjustments  are  quickly  made  by  means  of  thumb  wheels 
actuating  pinions  meshing  in  fixed  racks. 

The  whole  is  protected  by  a  cast-iron  cover  which,  when  raised, 
exposes  an  electric  light  for  illuminating  the  scales. 

Elevation  Quadrant. — To  save  time  in  bringing  the  mortar  to  the 
desired  elevation  and  to  avoid  inaccuracy  in  placing  the  quadrant  and 
holding  it  against  its  seat  a  special  elevation  quadrant  has  been  de- 
signed. This  quadrant  is  similar  to  the  gunner's  quadrant,  but  perma- 
nently attached  to  the  right  rim-base  of  the  mortar  and  consists  of  a 
bracket  with  a  toothed  arc  and  an  arm  hinged  at  the  other  end.  The 
arm  is  telescoped  and  its  front  bushing  carries  a  bubble,  a  microm- 
eter, and  a  toothed  sector  which  is  constantly  pressed  outward  by  a 
spiral  spring.  The  teeth  of  the  sector  engage  in  the  teeth  of  the  arc 
which  are  cut  in  degrees,  from  45  to  75  degrees.  The  micrometer,  which 
gives  a  limited  movement  to  the  arm,  is  graduated  to  a  least  reading 
of  1  minute.  The  cannoneer  at  the  right-handwheel  adjusts  the  quad- 
rant at  the  required  angle  of  fire  and  when  the  mortar  is  loaded  sets  its 
elevation  by  the  bubble. 

Lanyard     Attachment. — In  using  the  firing  mechanism,  model  of 


ARMAMENT  243 

1903,  at  high-angle  fire,  it  is  necessary  that  -the  direction  of  lanyard 
pull  shall  be  approximately  that  of  the  axis  of  the  piece  and  that 
the  lanyard  be  arranged  to  not  interfere  with  the  loading  opera- 
tions. 

A  short  lanyard  is  attached  to  the  underside  of  a  stopper  in  the 
top  of  the  racer  in  rear  of  its  central  opening  and  extends  below  a 
sheave  on  the  pit  ladder  •  and  thence  upward  to  the  firing  mech- 
anism. 

While  loading,  its  hook  is  placed  in  an  eye  screw  at  the  lower  edge 
of  the  breech. 

The  long  lanyard  is  hooked  into  the  eye  on  the  top  of  the  stopper 
and  the  stopper  and  short  lanyard  drawn  to  the  rear  to  fire. 

Electrical  Attachments. — These  consist  of  the  firing  circuit  inclosed 
in  flexible  metallic  conduit  and  with  its  safety  attachments  and  the 
illumination  circuit  also  inclosed. 

The  safety  firing  switch  is  designed  to  prevent  firing  the  mortar 
electrically  until  it  has  been  elevated  to  43  degrees.  It  consists  of 
a  circuit-breaker  attached  to  the  saddle  on  the  right  side  of  the  opening 
for  the  elevating  rack,  and  a  steel  cam  in  the  form  of  an  arc  of  a  circle 
subtending  40  degrees,  which  is  fastened  to  the  right  side  of  the  elevating 
arc.  The  circuit-breaker  holds  a  plunger,  which  is  constantly  pressed 
outward  by  a  spiral  spring,  breaking  the  circuit.  On  the  end  of  the 
plunger  is  a  roller  which,  when  the  mortar  is  elevated  43  degrees,  moves 
up  an  incline  on  the  cam,  pressing  the  plunger  and  closing  the  circuit. 
The  plunger  is  held  in  this  compressed  position  as  the  elevation  is  further 
increased  so  that  the  circuit  remains  closed  at  all  elevations  at  which 
the  mortar  is  fired. 

For  general  illumination,  hooded  16-candlepower  incandescent  lamps 
are  advantageously  placed,  the  usual  8-candlepower  candelabra  lamps 
being  placed  at  the  azimuth  circle  and  elevation  quadrant. 

All  electrical  conductors  enter  the  well  through  a  duct  in  the  con- 
crete, thence  they  hang  in  flexible  metallic  conduit  with  sufficient  slack 
to  permit  traversing  through  the  required  angle,  continuing  in  a  conduit 
system  of  wrought-iron  pipe,  junction-boxes,  etc.,  with  interior  insu- 
lation. 

Shot  Trucks  and  Shot  Tongs. — The  shot  trucks  (Fig.  11)  for  this 
carriage  are  constructed  so  as  to  admit  of  passing  the  shell  directly 
from  the  truck  into  the  mortar.  Each  truck  consists  of  a  light  rec- 
tangular framework  of  steel  mounted  on  four  rubber-tired  wheels  and 
carrying  a  pan,  in  which  the  shell  lies  horizontally  and  at  the  proper 
height  for  loading.  This  shell  pan  projects  to  the  front  and  is  designed 


244  THE  SERVICE  OF  COAST  ARTILLERY 

to  enter  the  breech  of  the  mortar  and  to  supply  the  place  of  the  usual 
loading  tray.  Two  straight  wooden  bars  which  slip  into  sockets  on 
each  side  of  the  truck  serve  as  handles  and  the  two  rear  wheels  are 
swiveled  to  facilitate  turning. 

Shot  tongs  are  also  provided  for  placing  the  projectile  on  the  shot 
trucks. 


CHAPTER    VI 
EXPLOSIVES,   PROJECTILES,  PRIMERS  AND  FUSES 

Explosives. — Explosives  are  divided  into  three  classes,  namely: 

Low  Explosives  or  progressive  or  propelling  explosives,  which 
include  those  used  as  propelling  agents  in  guns  or  mortars. 

High  Explosives  or  detonating  and  disruptive  explosives,  which 
are  used  in  shells,  torpedoes,  mines  and  for  demolitions  of  all  kinds. 

Fulminates  or  detonators  or  exploders,  which  are  related  to  high 
explosives  and  used  to  originate  explosive  reaction  in  the  first  two  classes. 

The  three  classes  are  distinguished  by  the  character  of  their  explosive 
reaction,  which  places  them  in  three  distinct  divisions  in  so  far  as  their 
action  is  concerned,  namely:  1.  Explosion  proper:  explosion  of  low 
order;  progressive  explosion;  combustion.  2.  Detonation:  explosion 
of  high  order.  3.  Fulmination:  a  characteristic  type  of  explosion 
produced  by  the  fulminates. 

Low  Explosives. — The  low  explosives  are  progressive  and  consist 
of  the  charcoal  powders  and  nitrocellulose  powders.  The  charcoal 
powders  are  divided  into  black  charcoal  powder  and  brown  charcoal 
powder. 

Black  Charcoal  Powder  has  the  following  ingredients:  75  parts 
by  weight  of  nitre  (saltpetre),  15  parts  by  weight  of  charcoal,  10  parts 
by  weight  of  sulphur. 

Nitre  is  a  salt  found  in  nature  as  an  incrustation  on  the  surface  of 
the  soil  in  certain  tropical  countries,  resulting  in  such  instances  from 
the  decomposition  of  organic  matter  in  the  presence  of  moist  alkaline 
earths.  The  decomposition  of  organic  matter  produces  ammonia,  which, 
combining  with  the  oxygen,  produces  nitric  acid.  The  acid,  acting 
on  other  salts  of  potassium,  produces  the  nitrate  which  in  solution 
percolates  through  the  soil  and  is  left  after  evaporation  as  an  incrusta- 
tion on  the  surface. 

Nitre  is  also  produced  artificially  by  the  nitre-bed  process.  A 
finely  mixed  lot  of  animal  and  vegetable  matter,  together  with  lime- 
stone, old  mortar,  wood  ashes  and  any  alkaline  material,  is  piled  in  a 
high,  narrow  bed  on  an  impervious  floor.  One  side  of  the  bed  is  exposed 

245 


246  THE  SERVICE  OF  COAST  ARTILLERY 

to  the  prevailing  wind,  and  the  opposite  side  is  terraced,  the  terraces 
inclining  toward  the  then  formed  gutters.  In  these  gutters  urine  from 
stables  is  thrown.  The  temperature  is  to  be  kept  between  60  and  70 
degrees  F.  The  chemical  action  above  described  takes  place  in  the 
body  of  the  heap  and  the  soluble  nitrates  percolating  through  the  mass 
of  the  heap  appear  after  evaporation  on  the  exposed  side  as  an  incrus- 
tation. 

The  crude  nitre  obtained  from  this  source  contains  the  nitrates  of 
magnesium  and  calcium  and  the  chlorides  and  sulphates  of  the  alkalies 
and  alkaline  earths.  Before  being  used  nitre  has  to  be  separated  from 
these.  This  is  accomplished  by  making  use  of  the  principle  of  the 
relative  solubilities  in  water  of  the  substances  at  different  temperatures. 
The  nitre  crystallizes  first  on  cooling,  leaving  the  impurities  in  solution. 
The  most  objectionable  impurity  of  those  mentioned  is  the  chlorides,  on 
account  of  their  hydroscopic  quality.  Nitre  should  always  be  freed 
from  them  and  before  being  used  is  always  tested  to  determine  if  they 
are  present.  . 

Nitre  is  distinguished  from  most  other  nitrates  by  the  form  of  its 
crystals,  which  are  long  six-sided  prisms;  and  from  most  salts  other  than 
nitrate  by  its  deflagration  when  heated  on  charcoal. 

The  value  of  nitre  in  explosives  is  due  to  the  fact  that  it  supplies 
oxygen  to  the  combustible  elements  present.  Five-sixths  of  its  oxygen 
is  available  for  its  combination  with  any  combustible,  the  nitrogen 
coming  off  from  its  decomposition  being  given  off  in  the  free  state. 
The  temperature  of  its  chemical  union  with  any  combustible  is  very 
high,  as  the  oxygen  is  supplied  in  very  concentrated  form  and  not 
mixed  with  nitrogen  as  in  the  case  of  air.  It  has  been  found  that  the 
amount  of  oxygen  in  a  cubic  inch  of  nitre  will  occupy  3023  cubic  inches 
at  atmospheric  pressure  and  temperature  of  60  degrees  F.  The  fact 
that  all  nitrates  used  in  explosives  act  as  carriers  of  oxygen,  and  break 
up  on  the  application  of  heat,  thus  increasing  the  temperature  of  the 
chemical  reaction,  makes  them  of  special  value  in  their  use  as  an  in- 
gredient of  explosives. 

Carbon  or  Charcoal  is  present  in  nearly  all  military  explosives.  Its 
function  in  all  cases  is  to  combine  with  oxygen,  forming  CO  or  CO2  or 
both,  the  combination  producing  an  elevation  of  temperature.  In 
explosive  mixtures  it  occurs  in  the  form  of  pulverized  charcoal. 

Charcoal  for  military  purposes  is  obtained  by  the  destructive 
distillation  of  wood,  such  as  willow,  alder,  dogwood  and  rye  straw. 
The  lighter  woods  are  preferable  and  are  usually  used.  The  charring 
is  done  in  a  metallic  cylinder  placed  in  a  retort  over  a  furnace  fire.  The 


EXPLOSIVES,  PROJECTILES,   PRIME KS  AND  FUSES  247 

effect  of  heat  is  to  drive  off  all  the  volatile  parts  of  the  wood,  as  wood 
naphtha,  water,  etc.  Charcoal  made  by  this  process  is  called  cylindrical 
charcoal  to  distinguish  it  from  the  common  pit  charcoal.  After  charring, 
the  charcoal  should  be  exposed  to  the  air  for  about  two  weeks  before 
grinding  up  for  powder.  The  reason  for  this  delay  after  charring  is 
the  danger  of  spontaneous  combustion.  About  30  per  cent,  of  the  weight 
of  wood  is  obtained  in  the  form  of  charcoal.  Charcoal  used  in  the 
manufacture  of  brown  powder  is  made  from  rye  straw  and  is  under- 
charred.  Freshly  charred  charcoal  pulverized  and 'stored  over  two 
feet  deep  will  ignite  spontaneously.  The  charcoal  used  in  black  powders 
contains  between  75  to  80  per  cent,  of  carbon,  3  to  5  per  cent,  of  hydro- 
gen, 10  to  23  per  cent,  of  oxygen  and  about  2  per  cent,  of  ash.  That  used 
in  the  manufacture  of  brown  powder  contains  45  to  48  per  cent,  of 
carbon,  5  per  cent,  of  hydrogen,  45  per  cent,  of  oxygen  and  the  remainder 
is  ash. 

Sulphur. — The  sulphur  used  is  that  commonly  found  in  the  volcanic 
districts  of  the  United  States,  Mexico  and  Italy.  It  is  usually  found  in 
chemical  combination  in  nature  in  the  sulphides  and  sulphates.  The 
common  ores  which  produce  sulphilr  are  those  of  iron  sulphates  (FeS), 
galena  (PbS),  zinc-blende  (ZnS),  black  sulphide  of  antimony  (Sb2S3) 
and  cinnabar  (HgS).  The  sulphur  is  obtained  from  these  native  ores 
and  from  iron  and  copper  pyrites  by  direct  distillation  and  subsequent 
refining  to  free  the  sulphur  from  impurities.  The  value  of  sulphur  as 
an  ingredient  of  gunpowder  is  that  it  reduces  the  temperature  of  ignition 
and  produces  in  the  chemical  union  with  oxygen  a  higher  temperature 
than  with  carbon,  as  well  as  increasing  the  rate  of  combustion  and 
pressure  of  the  gases  produced. 

MANUFACTURE. — As  a  preliminary  step  each  of  the  ingredients  is 
purified  and  then  pulverized  by  grinding.  The  charcoal  is  ground  in 
a  machine  resembling  a  large  coffee  mill,  and  the  nitre  and  sulphur 
in  a  mortar  mill.  The  latter  consists  of  a  pair  of  circular-edged  rollers 
traveling  around  a  circular  cast-iron  bed  and  revolving  about  a  com- 
mon horizontal  and  vertical  axis. 

The  nitre  or  sulphur  is  then  spread  evenly  over  the  bed  to  a  depth 
of  from  one  to  two  inches  and  reduced  to  a  fine  powder.  After  grinding, 
the  pulverized  material  of  each  kind  is  passed  through  a  sifting  reel 
which  consists  of  a  frame  cylinder  covered  with  wire  cloth,  32  meshes 
to  the  inch.  The  reel  is  revolved  slowly  until  the  particles  are  fine 
enough  for  incorporation.  The  remainder  is  reground. 

The  sifted  materials  are  weighed  out  in  the  relative  proportions 
given  above  and  placed  in  bags,  each  lot  weighing  50  pounds.  These 


248  THE  SERVICE  OF  COAST  ARTILLERY 

bags  are  then  taken  to. the  mixing  machine,  which  consists  of  a  copper 
drum  mounted  on  a  horizontal  shaft,  the  capacity  of  the  drum  being 
about  150  pounds.  The  shaft  of  the  drum  is  hollow  and  through  it 
passes  a  second  shaft  which  carries  a  series  of  arms  or  fliers,  and  revolves 
in  a  direction  opposite  to  that  of  the  first  shaft.  The  process  of  mixing 
takes  about  five  minutes.  The  mixed  material  is  placed  in  bags 
which  are  laid  on  their  side  to  prevent  the  ingredients  separating 
in  layers  according  to  their  specific  gravities.  They  are  handled 
carefully  in  transportation  without  jarring  or  shaking  for  this  same 
reason. 

The  ingredients  are  now  incorporated  in  the  incorporating  mill. 
This  is  the  most  important  step  of  the  whole  process,  the  object  being 
to  bring  the  ingredients  into  the  closest  possible  contact  so  that  each 
particle  of  the  resulting  cake  will  be  composed  of  all  the  ingredients  in 
their  proper  proportion. 

The  mixed  ingredients  are  spread  evenly  over  the  bed  of  the  mill, 
the  layer  being  not  more  than  one-half  nor  less  than  one-fourth  of  an 
inch  thick.  If  too  thick  the  incorporation  is  defective,  and  if  too  thin 
or  less  than  one-fourth  of  an  inch  in  thickness  there  is  danger  of  an 
explosion. 

After  the  charge  has  been  spread  over  the  bed  it  is  moistened  with 
distilled  water,  the  quantity  used  depending  on  the  state  of  the  atmos- 
phere. It  is  important  to  secure  a  uniform  moistening,  as  the  nature 
of  the  product  depends  much  upon  this.  The  time  for  incorporation 
is  from  three  to  four  hours  and  the  product  is  called  "  mill  cake." 
This  cake  should  have  a  uniform  blackish  gray  color  without  any  white 
or  yellow  specks. 

These  cakes  are  put  in  tubs  and  placed  in  small  magazines  where 
they  are  exposed  to  the  action  of  the  air  so  that  all  workings,  i.  e., 
several  charges,  may  contain  about  the  same  percentage  of  moisture — 
2  to  3  per  cent,  of  water  is  necessary  for  good  results  in  the  subsequent 
pressing 

So  far  as  the  chemical  requirements  are  concerned  the  process  is 
now  completed,  and  the  subsequent  operations  have  for  their  object 
physical  effects,  and  depend  upon  the  use  to  which  the  powder  is  to  be 
put.  In  order  that  it  may  have  its  rate  of  burning  regulated,  the  size, 
density  and  form  of  the  grain  must  be  fixed.  To  do  this  the  mill  cake 
is  now  taken  to  the  breaking-down  machine,  where  it  is  broken  up  into 
lumps  of  uniform  size.  The  breaking-down  machine  consists  essentially 
of  two  pairs  of  grooved  cylinders  arranged  one  pair  above  the  other. 
The  mill  cake  is  passed  through  these  rollers,  by  which  it  is  broken  up 


EXPLOSIVES,   PROJECTILES,  PRIMERS  AND  FUSES  249 

into  lumps  of  uniform  size.  The  product  after  leaving  the  breaking 
down  machine  is  called  "  powdered  meal." 

Now  in  order  to  granulate  the  powder  it  is  first  pressed  into  solid 
compact  cakes,  called  "  press  cakes."  This  is  done  in  a  hydraulic 
press,  which  consists  of  a  press  box — strong  gun-metal  box  having  three 
of  its  sides  hinged  and  an  hydraulic  ram.  In  filling  the  press  box  it  is 
laid  on  one  side  and  the  upper  side  laid  back,  the  metal  plates  being 
held  apart  in  a  frame.  The  powdered  meal  is  now  filled  in  between 
them,  the  side  is  closed  down  and  the  box  revolves  so  that  it  comes 
under  the  ram  of  the  hydraulic  press.  After  it  is  in  place  pressure  is 
applied  and  the  powdered  meal  compressed  in  a  hard,  compact  cake. 
Pressed  cake  is  then  broken  up  into  grains  by  passing  it  through 
the  granulating  machine.  This  machine  consists  of  a  series  of  tooth 
and  grooved  rollers,  the  clearance  between  which  and  the  character 
of  the  grooves  of  teeth  being  adjusted  for  the  kind  of  powder 
desired. 

Under  the  rollers  of  the  granulating  machine  are  arranged  three 
separate  screens.  The  upper  one  has  eight  meshes  to  the  inch,  the 
second  sixteen  and  the  third  is  a  copper  wire  cloth.  The  screens  have 
a  slight  slant  and  the  powder  collected  on  each  is  put  in  a  separate 
bin.  The  powder  caught  on  the  top  screen  is  too  large  and  is  reworked; 
that  on  the  second  screen  is  common  powder;  that  on  the  third  screen 
is  rifle  powder;  and  that  which  passes  through  the  lower  screen  is  powder 
dust. 

To  remove  the  sharp  corners  of  the  grains  and  to  free  it  from  the 
dust  the  powder  is  passed  through  the  dusting  machine.  This  consists 
of  horizontal  cylindrical  frames  covered  with  canvas  having  24  meshes 
to  the  inch.  Several  barrels  of  the  powder  are  placed  in  these  cylinders 
and  the  cylinders  revolved  at  about  40  revolutions  to  the  minute.  The 
dusting  process  requires  about  one-half  hour.  It  is  sometimes  desirable 
to  glaze  powder,  the  object  being  to  protect  the  grain  to  some  extent 
from  moisture  and  from  the  formation  of  dust  in  transportation. 
This  is  accomplished  by  placing  a  small  quantity  of  pulverized  graphite 
with  the  powder  grains  in  a  barrel-like  receptacle  and  revolving  the 
latter  for  a  short  time.  By  this  process  the  graphite  adheres  to  the 
powder  grains  and  forms  a  smooth  surface. 

The  final  operation  in  the  manufacture  of  black  powder  is  to  remove 
the  excess  of  moisture  by  drying.  This  is  done  by  spreading  the  powder 
out  over  shallow  canvas-bottomed  frames  arranged  in  tiers  over  a 
steam  radiator  and  subjected  to  a  temperature  of  130  degrees  F.  for 
about  eighteen  hours.  This  process  causes  the  production  of  some 


250  THE  SERVICE  OF  COAST  ARTILLERY 

dust,  and  the  powder  is  redusted.  Black  powder  is  packed  in  hundred- 
pound  packages.  For  commercial  use  oak  barrels  with  cedar  hoops 
are  used,  but  that  for  military  purposes  is  packed  in  the  zinc  powder- 
case  described  in  the  DEFINITIONS. 

Black  Prismatic  Powder  is  made  from  the  ordinary  black  granu- 
lated powder,  the  cannon  powder  grain  being  taken  as  a  base.  It  is 
made  by  reworking  the  black  powder  by  moistening  it  with  10  per  cent, 
of  water  and  forming  it  into  prisms  to  the  action  of  a  prism  p^ress.  This 
press  consists  essentially  of  two  sets  of  powerful  stamps  operating 
reciprocally  through  openings  in  a  heavy  mould  plate.  The  mould 
plate  has  a  series  of  hexagonal  moulds  in  it  and  is  placed  so  as  to  be 
horizontal  in  the  press.  The  bottoms  of  these  moulds  are  formed  by 
the  ends  of  the  lower  series  of  stamps,  each  of  which  has  seven  needles 
projecting  upwards  through  perforations  in  the  stamps.  The  upper 
series  of  stamps  has  also  similar  perforations.  The  powder  is  placed 
in  a  hopper  the  bottom  of  which  has  a  sliding  charging  plate  which 
contains  a  series  of  measures  corresponding  to  the  moulds  of  the  mould 
plate.  The  charging  plate  with  its  measures  filled  with  powder  slides 
over  the  mould  plate  until  the  measures  are  directly  over  the  moulds 
into  which  the  powder  drops.  The  charging  plate  then  slides  back. 
The  press  is  then  put  in  operation,  the  upper  stamps  descend  into  the 
moulds  and  the  needles  pass  up  into  the  perforations  of  the  upper 
stamps  and  form  the  perforations  of  the  prisms.  By  the  reciprocating 
action  of  the  press  when  the  upper  stamps  have  reached  their  lowest 
point  and  begin  to  ascend,  the  lower  stamps  follow  them  up  until  the 
ends  of  the  lower  stamps  are  flush  with  the  top  of  the  mould  plate  and 
the  upper  end -perforating  needles.  When  this  position  is  reached  the 
lower  stamps  stop  and  the  upper  ones  continue  upward,  leaving  pris- 
matic grains  free  to  be  pushed  off  by  the  edge  of  the  charging  plate 
as  it  returns  carrying  a  new  charge. 

Sphero-hexagonal  Powder  is  a  black  powder  made  in  a  similar 
way  as  the  prismatic  powder  just  described.  It  receives  its  name 
from  the  form  of  the  grain,  which  consists  of  two  half  spheres  with 
a  narrow  six-sided  hexagonal  prism  at  the  diameter. 

Brown  Charcoal  Powder  has  the  following  ingredients:  80  parts 
by  weight  of  nitre,  16  parts  by  weight  of  charcoal,  3  parts  by  weight  of 
sulphur  and  1  part  by  weight  of  moisture.  The  charcoal  is  made  of 
rye  straw  and  is  under-charred.  The  color  of  the  powder,  which  is  a 
brown  or  cocoa  color,  is  due  to  this  fact.  The  method  of  manufacture 
and  the  ingredients  are  the  same  as  described  for  the  manufacture  of 
black  charcoal  powder.  Brown  powder  burns  more  slowly  than  black 


EXPLOSIVES,   PROJECTILES,   PRIMERS   AND  FUSES  251 

powder,  and  with  lower  pressure  in  the  chamber  of  the  gun.  The 
explosion  is  more  uniform  and  the  stresses  produced  in  the  bore 
of  the  gun  are  not  so  great,  thus  increasing  the  endurance  of  the 
gun. 

Brown  Prismatic  Powder  is  made  in  exactly  the  same  way  as  that 
described  for  black  prismatic  powder,  the  brown  granulated  powder 
being  taken  as  the  base. 

Nitrocellulose  or  Smokeless  Powder  is  an  explosive  compound.  It 
is  distinguished  from  an  explosive  mixture  like  the  charcoal  powders 
in  which  the  ingredients  are  mixed  mechanically,  in  that  the  con- 
stituents are  brought  together  through  a  chemical  reaction.  The 
word  powder  is  misleading  as  applied  to  modern  propellants,  in  that 
they  are  made  in  a  variety  of  forms  which  do  not  bear  any  resemblance 
to  a  powder,  but  take  the  shape  of  tubes,  cord,  strips,  flakes  or 
cubes. 

Nitrocellulose  is  the  base  of  all  smokeless  powders.  Its  molecule 
contains  carbon,  hydrogen  and  oxygen,  so  that  when  conditions  favor- 
able to  the  combination  of  these  elements  are  produced,  the  gaseous 
oxides  of  carbon  and  water  vapor  are  formed. 

Any  substance  whose  molecules  contain  carbon,  hydrogen  and  oxy- 
gen in  the  proportion  to  give  CO,  or  CO2  and  H2O  may  become  an 
explosive.  One  wThich  is  so  constituted  and  at  the  same  time  has  weak 
molecular,  bonds  due  to  the  presence  of  some  other  element  or  radical, 
is  an  explosive. 

The  principal  ingredients  of  nitrocellulose  powder  consist  of 
cellulose,  nitric  acid,  sulphuric  acid,  ether  and  alcohol.  The  manu- 
facture of  nitrocellulose  powder  consists  of  the  following  essential 
steps : 

Cleaning. — The  cotton  waste  or  cotton  rags  are  brought  into  the 
washing  house  in  large  bales.  These  are  broken  open  and  put  into 
the  washer.  This  consists  of  a  large  iron  tank  with  pipes  running 
through  the  center.  The  tank  is  filled  with  a  solution  of  caustic  soda, 
and  the  cotton  waste — about  175  pounds  of  caustic  soda  to  200  pounds 
of  the  cotton  waste.  The  washer  is  slowly  revolved,  keeping  the 
mass  constantly  agitated.  The  temperature  is  retained  at  120  to 
130  degrees  F.,  and  the  washing  continues  for  four  hours,  the  object 
being  to  remove  any  oil  or  grease  from  the  waste  or  rags.  After  being 
washed  for  four  hours  the  product  is  taken  from  the  washhouse  to  the 
centrifugal  wringer  and  wrung  as  dry  as  possible,  after  which  it  is 
returned  to  the  washer  and  washed  in  clear,  pure  water.  It  is  then 
wrung  out  a  second  time  in  the  centrifugal  wringer  and  taken  to  the 


252  THE  SERVICE  OF  COAST  ARTILLERY 

picker,  which  consists  of  two  horizontal  toothed  cylinders  revolving 
in  opposite  directions.  The  cotton  waste  is  then  placed  on  a  wooden 
apron  arid  fed  into  the  picker,  which  tears  it  apart,  removing  all  knots 
and  tangles  and  delivers  it  in  finely  shredded  strips  about  an  inch  long 
and  one-quarter  of  an  inch  wide. 

Drying. — The  cotton  from  the  picker  is  collected  in  boxes  and 
taken  into  the  drying  house,  where  it  is  placed  in  large  wooden  bins 
having  perforated  bottoms.  Hot  air  at  a  temperature  of  90  to  105 
degrees  C.  is  forced  up  through  the  bins  as  the  cotton  is  turned  from 
time  to  time  by  hand.  The  process  of  drying  requires  about  eight 
hours,  at  the  end  of  which  time  the  cotton  should  not  contain  more 
than  five-tenths  of  one  per  cent,  of  water. 

Nitrating. — The  cotton,  having  been  dried,  is  placed  in  air-tight 
cans  and  taken  to  the  nitrating  house.  The  object  of  packing  it  in  air- 
tight cans  is  to  prevent  the  dry  cellulose  from  absorbing  water  from 
the  air.  The  nitrating  is  done  in  a  centrifugal  machine.  One  can 
of  the  dry  cotton,  containing  about  16  pounds,  is  placed  in  the  nitrating 
machine  with  900  pounds  of  mixed  acids  consisting  of  50  per  cent, 
sulphuric  and  28  per  cent,  nitric.  The  mixed  acids  are  drawn  from 
a  large  tank  called  the  mixed  acid  tank.  The  charge  is  kept  in  the 
nitrating  machine  for  about  30  minutes,  during  which  time  it  is  turned 
over  with  iron  forks.  In  becoming  nitrated  the  cotton  increases  in 
weight  about  one-half,  the  16  pounds  of  cellulose  giving  about  24  pounds 
of  nitrocellulose.  It  will  be  noted  that  the  process  of  nitration  changes 
the  cotton  or  cellulose  into  nitrocellulose  or  cellulose  nitrated.  The 
powder  contains  about  12.6  per  cent,  of  nitrogen  as  well  as  free  acids  and 
alkali  used  in  the  manufacture,  and  some  unnitrated  cellulose.  At 
the  end  of  30  minutes  the  drain  cocks  of  the  nitrating  machine  are 
opened,  the  machine  started,  and  spent  acid  forced  out  by  centrifugal 
action. 

Purification. — The  rest  of  the  process,  which  is  very  essential  to 
the  production  of  stable  smokeless  powder,  consists  in  removing  the 
impurities  left  in  the  nitrocellulose  in  the  manufacture.  The  free 
acids  and  unstable  nitro  by-products  must  be  removed  in  order  that 
the  nitrocellulose  may  be  kept,  even  in  the  dry  state,  at  ordinary 
temperature  without  deterioration.  Nitrocellulose  is  taken  at  once 
from  the  nitrating  machine  and  immersed  in  a  large  quantity  of  pure 
water,  and  left  there  for  eight  hours,  two  changes  of  water  being  made 
during  that  time.  It  is  then  taken  to  the  centrifugal  machine  and, 
while  revolved  in  this,  cold  water  is  played  upon  it  with  a  hose  for 
about  ten  minutes.  The  machine  is  then  revolved  at  its  highest  speed 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  253 

and  the  nitrocellulose  wrung  as  dry  as  possible.  When  about  1,000 
pounds  has  been  treated  in  this  manner,  it  is  given  a  definite  number 
known  as  its  "lot  number/'  which  it  retains  throughout  its  manu- 
facture, and  all  subsequent  operations  are  recorded  in  reference  to  this 
number.  The  size  of  a  lot  may  sometimes  vary,  depending  upon  the 
place  of  manufacture.  The  lot  is  now  taken  to  the  purifying  tanks, 
which  are  large  wooden  tanks  with  steam  pipes  arranged  over  the 
bottom.  Steam  circulates  through  these  pipes  and  keeps  the  cellulose 
znd  water  at  the  desired  temperature.  Pure  water  is  put  in  the  tank 
and  one  lot  put  in.  The  lot  is  kept  in  the  purifying  tanks  for  two 
days,  the  temperature  being  kept  at  80  degrees  C.,  and  the  water  is 
renewed  three  times  during  this  period.  At  each  renewal  the  tempera- 
ture is  increased  to  100  degrees  C.  for  2  hours.  The  mass  is  kept 
agitated  by  revolving  arms  set  at  different  angles.  From  the  purify- 
ing tanks  the  nitrocellulose  is  taken  to  the  centrifugal  machine,  where 
it  is  washed  with  pure  cold  water  from  a  hose  for  ten  minutes.  It 
then  goes  to  the  pulper. 

Pulping. — The  pulper  is  an  ordinary  pulping  machine  used  in  paper 
mills.  It  consists  of  an  oval-shaped  vat  or  tank  with  a  horizontal 
shaft  passing  across  its  narrowest  dimension.  On  one  end  of  this 
shaft  is  a  drum  which  has  on  its  outer  surface  a  series  of  parallel  knife 
edges.  Directly  below  the  drum  is  a  concentric  surface  with  a  second 
series  of  knife  edges.  Pure  water  circulates  slowly  throughout  the  vat, 
running  in  at  one  point  and  overflowing  at  the  other.  From  600  to 
1,000  pounds  of  nitrocellulose  from  the  purifying  tank  is  placed  at  one 
time  in  the  pulper.  The  drum  in  revolving  pulls  the  cotton  down  and 
forces  it  between  the  two  series  of  knife  edges,  cutting  it  finer  and 
finer  until  the  whole  mass  is  a  smooth,  even,  fine  pulp,  about  the  con- 
sistency of  corn  meal.  This  requires  about  six  hours.  The  contents 
of  the  vat  are  submitted  to  an  acid  test  from  time  to  time,  to  determine 
if  any  free  acid  is  being  liberated  as  the  pulping  proceeds.  Should 
the  test  show  the  presence  of  free  acid,  sufficient  sodium  carbonate 
is  added  to  neutralize  the  acid. 

Poaching. — The  poacher  consists  of  a  large  deep  cylindrical  vat 
with  a  propeller-shaped  wheel  on  a  vertical  axis  near  its  bottom.  Steam 
pipes  are  placed  over  the  bottom.  The  cotton  is  taken  from  the 
pulper  and  put  in  the  poacher,  and  subjected  to  the  action  of  a  boiling 
carbonate  of  soda  solution.  It  is  then  rewashed  in  cold  water  as  in 
the  purifying  vats,  the  process  continuing  for  three  days,  having  twelve 
changes  of  water,  and  two  hdurs  boiling  at  each  change.  The  propeller 
keeps  the  mass  circulating  throughout  the  entire  process.  The  iiitro- 


254  THE  SERVICE  OF  COAST  ARTILLERY 

cotton  is  then  taken  from  the  poacher  and  dumped  into  a  large  volume 
of  pure  cold  water  which  is  contained  in  a  large  trough.  An  endless 
belt  of  coarse  cotton  cloth  which,  at  some  distance  outside  of  the 
trough,  passes  between  two  rollers,  circulates  through  the  trough.  As 
the  belt  moves  through  the  mass  of  suspended  cotton  a  certain  quantity 
adheres  to  it,  and  the  belt  carries  this  up  through  the  rollers,  which 
squeeze  out  the  surplus  water.  The  cotton  is  detached  Trom  the  belt 
by  a  scraper,  and  falls  into  receptacles  placed  on  the  other  side  of  the 
rollers.  The  cotton  is  now  in  the  form  of  small  thin  flakes  and  is 
called  "pyro,"  and  contains  about  58  per  cent,  of  water.  At  this 
point  it  is  submitted  to  careful  laboratory  tests.  If  this  mass  was 
now  compressed  into  blocks  it  would  be  in  the  usual  form  of  gun- 
cottori. 

Dehydrating. — The  pyro  is  now  taken  to  the  dehydrating  press 
and  the  water  is  extracted  by  means  of  alcohol,  which  is  forced  through 
the  pyro  by  air  pressure,  the  alcohol  displacing  the  water.  Sufficient 
alcohol  is  left  in  the  cotton  to  accomplish  its  colloidization,  when  ether 
is  added  in  the  next  operation.  About  15  pounds  of  pyro  is  placed  in 
the  cylinder  of  the  dehydrating  press  and  subjected  to  a  pressure  of 
200  pounds  to  the  square  inch.  This  forms  it  into  a  cylindrical  cheese. 
Not  all  of  the  water  is  forced  out  by  this  pressure,  so  about  14  pounds 
of  alcohol  is  let  into  the  cylinder.  Air  is  now  admitted  over  the  alcohol 
and  subjected  to  a  pressure  of  100  pounds  to  the  square  inch.  This 
forces  the  alcohol  through  the  pyro,  the  liquid  flowing  out  through  the 
pipe  below.  First  water  comes  out,  then  a  mixture  of  water  and 
alcohol,  and  finally  alcohol  of  full  strength.  A  pressure  of  3,000  pounds 
per  square  inch  is  now  put  on  the  cheese,  and  more  of  the  alcohol  forced 
out,  enough  remaining,  however,  for  colloiding. 

Colloidization. — The  pyro-cheese,  weighing  about  17  pounds, 
is  taken  from  the  dehydrating  press  to  the  colloiding  machine,  which 
is  an  ordinary  kneading  machine.  Three  of  the  pyro  cheeses  are 
broken  up  and  put  into  the  kneader  with  about  one-half  of  their  weight 
of  ether.  The  kneader  is  started  and  the  charge  is  mixed  until  all  the 
ether  is  absorbed,  which  as  a  rule  requires  about  two  hours.  At  the 
end  of  this  time  the  colloiding  is  finished,  and  the  product  should  be 
a  smooth  compact  colloid  with  a  clear  amber  or  light-brown  color. 
The  colloid  is  pressed  into  a  cake  by  hydraulic  pressure,  and  should 
show  a  few  white  spots  when  finished,  which  are  caused  by  air 
bubbles. 

Granulation. — The  colloid  cake  is  now  put  through  the  macaroni 
press,  which  is  a  hydraulic  press  having  small  holes  in  the  bottom  of 


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256  THE  SERVICE  OF  COAST  ARTILLERY 

its  cylinder.  The  .colloid  is  forced  by  a  pressure  of  500  pounds  through 
these  small  holes  and  falls  in  a  receptacle  below  in  macaroni-like  strings. 
The  object  of  this  operation  is  to  free  the  colloid  from  air  bubbles 
and  to  blend  it  better.  The  macaroni-like  strings  are  collected  and  put 
into  the  final  press,  where  they  are  pressed  into  a  cake^  known  as  the 
powder  cake.  The  powder  cake  is  put  through  the  die  press,  which  is 
a  horizontal  press  with  a  cone-shaped  cylinder,  into  the  apex  of  which 
is  fitted  the  die  with  needles  of  the  proper  size  for  the  perforation. 
The  continuous  pressure  forces  the  colloid  into  the  cone  and  out  through 
the  die,  the  needles  making  the  perforations.  The  rope-like  cylinder 
of  the  diameter  of  t]jie  powder  grain  is  carried  on  rollers  along  the  table 
on  which  the  press  rests,  until  it  reaches  a  point  where  it  is  cut  into 
grains  of  the  proper  length  by  a  revolving  disc.  The  die  can  be  changed 
so  that  any  size  grain  may  be  formed. 

Drying. — The  grains  from  the  die  press  are  collected  in  cans  with 
woven  wire  bottoms  and  are  taken  to  the  solvent-recovery  house, 
where  hot  air  is  forced  up  through  the  grains.  This  hot  air  carries 
off  a  portion  of  the  solvent,  and  the  grains  shrink  accordingly.  The 
powder  is  now  taken  to  the  dry  house,  where  it  kept  from  two  to  four 
months  in  a  drying  temperature  from  100  to  105  degrees  F. 

Lot  Number. — A  record  is  kept  of  each  "pyro  lot,"  and  several  of 
these  lots  are  allowed  to  accumulate,  after  which  they  are  blended 
and  receive  a  "lot  number."  The  blend  lot  number  is  indexed  and  is 
that  which  reaches  the  service. 

Cordite. — This  is  a  British  smokeless  powder  composed  of  37  parts 
guncotton,  58  parts  nitro-glycerine,  and  5  parts  vaseline.  This  powder 
gives  very  high  muzzle  velocities  with  low  pressures,  but  the  temperature 
of  its  explosion  is  so  high  as  to  cause  a  rapid  erosion  of  the  bore.  For 
this  reason  the  percentage  of  nitroglycerine  has  gradually  been  reduced 
and  the  result  is  given  in  the  new  powder  called  "Cordite  M.  B."  which 
contains  58  parts  guncotton,  37  parts  nitroglycerine  and  5  parts 
vaseline. 

Brown  Prismatic  Powder  may  be  used  in  the  8-,  10-,  and  12-inch 
rifles  and  the  12-inch  mortars.  As  this  powder  rapidly  deteriorates 
it  may  be  necessary  to  increase  the  charge  to  the  capacity  of  the 
chamber  to  obtain  the  proof  velocity.  This  involves  the  building  up 
of  charges,  the  operation*  of  which,  in  the  case  of  this  powder,  consists 
of  stringing  the  grains  on  wires  to  make  the  required  height  of  the  charge, 
as  shown  in  the  following  table: 


EXPLOSIVES,  PROJECTILES,   PRIMERS  AND  FUSES 


257 


Length  of 

I 

Section 
(Number  of 

Full  Charge. 

Maximum 
Charge. 

1. 

Prisms.) 

u  * 

g 

g 

A 

.s  .  s 

.4 

.S  ,  « 

|6 

s 

•*>  c 

got 

|| 

ill 

3.5 

3 

03 

'53  ^ 

.^6^ 

.20  w 

fe 

i 

a 

J 

AH 

f 

* 

8-inch  breech-loading  rifle      . 

2 

23 

24 

135 

31 

154 

34 

2 

30 

31 

280 

48 

320 

55 

/    3 
1*1 

18 
18 

1-8 
19 

380 
110 

76 
61 

450 
110 

85 
61 

12-inch    breech-loading    mortar,   cast- 

iron  hooped                    

1 

14 

75 

61 

81 

61 

12-inch  breech-loading  mortar 

1 

19 

105 

61 

110 

61 

*  Cone  Section. 

After  the  charges  are  built  up  the  black  powder  priming  charge  is 
placed  in  position  on  top  of  the  charge  and  the  serge  silk  bags  slipped 
down  over  the  form.  The  charge  is  then  inverted  and  another  priming 
charge  placed  on  what  is  now  the  top.  The  bag  is  then  sewed  up  with 
silk  thread;  then  weighed;  and,  in  the  case  of  mortars,  the  zone 
number  marked  thereon. 

For  brown  prismatic  powder  either  one  of  two  forms  of  igniter  may 
be  used,  namely:  1.  Seven  black  prisms  in  the  center  of  the  bottom 
layer  of  each  section  of  the  cartridge.  With  this  igniter  the  bottom 
of  the  bag  next  to  the  vent  must  be  cut  when  loaded  to  insure  ignition. 
2.  In  this  case  the  bag  is  made  with  a  double  bottom;  the  outside 
thickness  is  of  the  same  cloth  as  the  bag,  but  the  inside  thickness  is 
of  a  lighter  cloth  such  as  that  used  in  field  and  siege  cartridges.  About 
2  ounces  of  rifle  powder  for  the  8-inch  rifle  and  3  ounces  for  the  10-  and 
12-inch  sections  are  spread  between  these  two  bottoms,  more  thickly 
toward  the  middle,  the  bottom  is  then  quilted  in  about  1-inch  squares 
to  retain  the  powder  in  place. 

Each  lot  of  powder  or  cartridge  issued  is  marked  for  the  weight  of 
charge  and  proof  velocity  and  pressure;  these  are  to  be  considered  the 
standard  for  that  powder,  unless  subsequent  changes  are  announced 
in  orders.  The  propelling  charges  of  smokeless  powder  for  both  the 
reserve  supply  and  target  practice  are  issued  in  hermetically  sealed 
cartridge  storage  cases. 

No  changes  in  these  powder  charges  are  allowable  without  the  ex- 
press authorization  contained  in  orders  or  in  instructions  from  the 
€hief  of  Ordnance.  Changes  in  charges  should  always  be  made  with 


258  THE  SERVICE  OF  COAST  ARTILLERY 

care,  even  when,  by  calculation,  the  pressures  appear  to  be  within 
the  safe  limits.  All  lots  of  smokeless  powder  that  have  been  tested 
in  recent  years,  except  those  specially  noted,  have  been  adjusted  to 
give  the  prescribed  muzzle  velocity  when  fired  at  the  standard  temper- 
ature of  70  degrees  F.  When  powder  is  used  at  any  other  temperature 
than  that  of  the  standard,  correction  must  be  made  therefor.  See 
"Powder  chart."  In  some  of  the  earlier  tests  of  lots  of  smokeless 
powder,  only  the  temperature  of  the  air,  and  not  that  of  the  powder 
at  the  time  of  firing  was  recorded. 

To  avoid  irregular  and  sometimes  excessive  pressures,  the  total 
length  of  charge  of  guns  should  really  equal  the  length  of  chamber,, 
and  should  never  be  less  than  9/10  of  that  length.  When  reduction 
of  the  charge  is  found  necessary  care  must  be  taken  that  the  new 
cartridge  made  is  firm  and  that  the  bag  is  of  the  necessary  diameter 
and  uniform  over  its  length.  The  requirement  as  to  length  of  charge 
is  not  necessary  in  the  case  of  mortars. 

Smokeless  powder  may  be  used  in  all  types  of  guns.  Before  build- 
ing up  charges  of  smokeless  powder  or  before  using  those  that  are 
issued  already  built  up  it  is  necessary  that  the  entire  amount  of  powder 
to  be  used  is  thoroughly  blended. 

Blending. — The  method  of  blending  powder  just  prior  to  its  use 
is  as  follows :  A  suitable  floor  space  is  first  covered  with  paulins  around 
the  outer  edge  of  which  are  placed  boards  (1x12  inches),  supported  by 
brackets  to  keep  them  in  place  and  prevent  the  powder  from  scattering. 
All  the  powder  to  be  used  is  taken  from  the  cases  and  bags,  and  placed 
in  a  single  pile  in  the  center  of  the  covered  space.  Ten  men,  provided 
with  wooden  shovels,  form  10  circumferential  piles  by  shoveling  care- 
fully from  the  bottom  of  the  large  center  pile  to  the  tops  of  the  10 
smaller  piles  until  the  center  pile  is  exhausted.  The  powder  from  the 
10  small  piles  is  then  shoveled  from  the  bottom  of  each  to  the  top  of 
the  large  center  pile,  each  shovelful  being  scattered  over  the  pile  as 
much  as  possible  during  the  operation.  The  operation  of  shoveling 
from  the  center  pile  to  the  10  small  piles  and  back  again  forms  one 
cycle  of  the  blending  process,  and  to  thoroughly  blend  a  lot  of  powder 
requires  5  cycles. 

Nitroglycerin  and  nitrocellulose  powders  must  not  be  blended 
together.  Each  charge  should  always  be  made  up  from  the  same 
lot  of  powder. 

In  blending  smokeless  powder  it  should  not  be  done  in  the  direct 
rays  of  the  sun. 

Only  powders  of  the  same  lot  are  blended  together.     Charges  for  a, 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES 


259 


given  zone,  weight  of  projectile  or  model  of  gun,  should  not  be  changed 
for  any  other  zone,  weight  of  projectile  or  model  of  gun. 

With  nitrocellulose  and  nitroglycerin  powder  charges,  the  bag  is 
opened  and  the  powder  charge  shoveled  in.  The  section  is  then  laid 
on  a  table  and  rolled  to  get  it  as  compact  as  possible  before  beginning 
to  lace  it.  To  avoid  bulging  in  the  center,  the  lacing  is  commenced 
at  the  middle  and  carried  towards  each  end,  in  order  to  keep  the  section 
of  uniform  diameter. 

In  lacing,  place  the  point  of  the  needle  close  to  and  outside  the  seam 
or  plait,  letting  the  needle  come  out  between  it  and  the  expansion 
plait  and  pass  over  the  latter;  lace  from  left  to  right  and  right  to  left, 
taking  stitches  about  one  and  one-half  inches  apart.  After  lacing 
about  4  inches  of  the  length  of  the  bag,  draw  the  lacing  taut  and  tie 
the  twine,  so  that  if  the  twine  should  break  in  handling,  the  section 
cannot  lose  more  than  4  inches. 

Cartridge  bags  for  5  and  6-inch  rapid-fire  guns  have  no  extension 
plait. 

The  dimensions  of  the  sections  of  cartridges  of  smokeless  powder 
made  up  with  the  average  charges  of  powder  are  given  in  the  following 
table : 


Charge. 
Pounds. 

Cartridge  (or  Section.) 

Number 
of 
Sections. 

Diameter, 
Inches. 

Length, 
Inches. 

5-inch  rapid-fire  gun,  model  1897  
5-inch  rapid-fire  gun,  model  1900  
6-inch  rapid-fire  gun,  model  1897  
6-inch  rapid-fire  gun,  models  1900,  1903  and 
1905 

16.4 
23.0 

29.7 

39.1 
80.0 
155.0 
205.0 
275.0 
325.0 
33.0 
62.0 

1 
1 

1 

1 

2 

2 

2 

4 
4 
1 
1 

5.25 
5.75 
6.00 

6.90 
8.25 
10.25 
12.00 
*  12.25 
f  14.00 
10.75 
12.00 

27.00 
34.50 
32.00 

41.00 
24.00 
30.00 
J  33.00 
18.25 
§20.25 
15.00 
20.00 

8-inch  rifle  
10-inch  rifle,  models  1888  and  1895  

10-inch  rifle,  model  1900  
12-inch  rifle,  models  1888  and  1895  

12-inch  rifle,  model  1900  
12-inch  mortar,  cast-iron,  hooped  

12-inch  mortar,  steel  

*  12.25  to  13. 


t  14  to  14.5. 


I  33  to  35. 


20.25  to  21.25. 


Igniting  Charges. — These  charges  are  composed  of  black  rifle 
powder.  As  explained  above  they  are  placed  in  position  at  each  end 
of  the  sections  of  the  charge,  their  function  being  to  properly  ignite 
the  less  inflammable  charge  of  smokeless  powder. 


260  THE  SERVICE  OF  COAST  ARTILLERY 

The  weight  of  igniting  charges  will  be  found  in  the  table  of  weights 
of  powder  charges,  etc.,  on  page  255. 

Blank  Ammunition. — Blank  ammunition  is  used  in  firing  salutes, 
for  maneuver  firings,  and  for  the  morning  and  evening  gun,  and  for 
instruction  purposes. 

All  firings  with  blank  ammunition,  whether  with  breech  or  muzzle- 
loading  guns,  is  under  the  personal  supervision  of  a  commissioned 
officer  who  is  present  at  the  firing  and  directs  it.  Whenever  more  than 
1  round  is  fired  from  any  gun  or  guns  he  sees  that  the  chamber  of 
breech-loading  guns  and  the  bore  of  muzzle-loading  guns  is  carefully 
sponged  out  with  a  damp  sponge,  to  extinguish  sparks  and  remove 
powder  residue  after  each  round  and  before  the  insertion  of  another 
round. 

Care  must  be  exercised  to  see  that  the  sponges  are  not  worn  and 
that  they  thoroughly  fill  the  chamber  or  bore.  The  interval  between 
rounds  of  blank  ammunition  should  be  sufficient  to  allow  thorough 
sponging  of  the  chamber  or  bore  and  examination  to  ascertain  that  all 
sparks  have  been  extinguished. 

Guns  using  metallic  ammunition  are  employed  whenever  practicable 
in  firing  blank  ammunition;  in  their  absence  breech-loading  guns 
using  loose  ammunition  should  preferably  be  used. 

Muzzle  loaders  are  used  only  when  breech  loaders  are  not  available. 
When  using  muzzle-loading  guns  a  sufficient  number  should  be  employed 
to  avoid  the  necessity  of  firing  the  same  gun  until  a  reasonable  interval 
has  elapsed. 

The  cartridge  bags  for  muzzle-loading  guns  or  breech-loading  guns 
not  using  fixed  ammunition  are  of  silk,  chemically  treated  to  make 
it  as  non-inflammable  as  possible,  and  the  cartridges  are  made  to  measure 
in  length  at  least  1^  times  the  diameter. 

It  has  been  found  difficult  to  tie  the  open  end  of  the  cartridge  bags 
heretofore  used  for  blank  charges  in  such  a  manner  as  to  prevent  that 
end  opening  and  permitting  powder  grains  to  leak  out.  The  cartridge 
bags  now  issued  have  both  ends  alike.  There  is  an  opening  left  between 
the  circular  disk  forming  the  front  end  of  the  bag  and  the  body,  which 
should  be  closed  by  sewing  after  the  charge  has  been  inserted. 

The  post  ordnance  officer  before  issuing  cartridges  for  blank  am- 
munition firing  to  organizations  sees  that  the  bags  are  in  sound  condi- 
tion and  that  no  powder  can  escape  therefrom,  and  the  bags  are  inspected 
further  as  to  their  condition  in  this  respect  by  the  commissioned  officer 
in  charge  of  the  firing  before  their  use. 

Unless  all  the  above  conditions  be  fulfilled  blank  ammunition  should 


EXPLOSIVES,   PROJECTILES,   PRIMERS  AND  FUSES  261 

not  be  fired  with  breech-loading  guns  using  non-metallic  ammunition 
or  with  muzzle-loading  guns. 

Blank  metallic  ammunition  for  saluting  and  maneuver  purposes 
is  assembled  at  posts.  For  this  purpose  there  are  issued  saluting 
cartridge  cases,  saluting  powder  in  bulk,  tight-fitting  felt  wads,  primers, 
adapters,  etc.;  also  reloading,  decapping,  and  cleaning  outfits.  The 
cartridge  cases  are  issued  unprimed,  with  primers  in  separate  moisture- 
proof  tin  boxes,  and  are  not  primed  until  just  before  inserting  the 
powder  charge  and  the  wad.  Cartridge  cases  should  never  be  primed 
after  the  powder  charge  has  been  inserted. 

The  same  care  must  be  exercised  in  sponging  the  chamber  with  guns 
using  metallic  ammunition  as  with  guns  using  non-metallic  ammunition. 

Saluting  cartridge  cases  for  6-pounder,  15-pounder,  4-inch,  4.72-inch, 
and  6-inch  guns  may  be  distinguished  from  service  cartridge  cases  by 
the  fact  that  they  are  considerably  shorter  than  the  service  case. 
Service  cases  of  the  above  calibers  will  under  no  consideration  be  used 
in  the  preparation  of  blank  ammunition.  For  all  other  guns  using 
metallic  ammunition  the  service  case  and  the  saluting-cartridge  case 
are  the  same. 

Primers  will  not  be  removed  from  the  hermetically  sealed  cases  in 
which  they  are  received  until  they  are  to  be  used.  They  are  made  a 
tight  fit  in  the  primer  seat  of  the  cartridge  case,  and  should  be  pressed 
into  place  with  the  inserting  press  and  not  hammered  in. 

In  preparing  saluting  ammunition  the  following  instructions  must 
be  observed: 

(a)  Before  assembling,  the  saluting  case  should  be  inspected  to  see 
that  it  is  thoroughly  clean  and  dry.     The  primer  will  then  be  inserted 
with  the  inserting  press ;   after  which  the  proper  weight  of  loose  powder 
will  be  poured  into  the  case  and  shaken  down. 

(b)  A  felt  wad  will  next  be  inserted  and  pressed  down  hard  until 
it  rests  squarely  on  the  powder  charge. 

(c)  The  wad  will  then  be  made  fast  to  the  cartridge  case,  to  prevent 
its  being  dislodged  in  handling,  in  the  following  manner:    Pour  rub- 
berine  paint  upon  the  surface  of  the  wad  and  case  until  it  forms  a  layer 
over  the  surface  about  a  sixteenth  of  an  inch  thick.     Allow  the  case 
to  stand  from  10  to  20  minutes,  until  the  paint  has  dried  and  been 
partly  absorbed  by  the  wad.     Then  pour  in  an  additional  amount  of 
paint  around  the  edges  of  the  wad  to  entirely  seal  the  joint  between 
the  wad  and  the  cartridge  case,  and  also  to  form  a  layer  on  the  side  of 
the  cartridge  case  from  .02  to  .03  of  an  inch  in  thickness. 

The  rubberine  paint  is  very  tough  and  strongly  adhesive,  and  if 


262 


THE  SERVICE  OF  COAST  ARTILLERY 


used  as  directed  will  prevent  danger  of  wads  dropping  out  in 
handling. 

The  wads,  when  issued,  are  a  tight  fit  in  the  cartridge  case  for  which 
they  are  intended.  If,  after  storage,  it  is  found  that  any  have  shrunken 
so  as  to  fit  loosely  they  should  not  be  used,  but  a  report  on  their  condition 
made  to  the  proper  authority  in  order  that  they  may  be  replaced. 

If  rubberine  paint  is  not  available,  any  other  quick-drying  paint 
issued  by  the  Ordnance  Department  for  coating  cavities  of  projectiles 
may  be  used  instead. 

Blank  ammunition  for  saluting  purposes  and  for  morning  and 
evening  gun  should  be  made  up  in  lots  of  25  cartridges  (the  number 
of  primers  contained  in  a  box),  but  a  new  lot  should  not  be  made  up 
until  two  or  three  days  before  the  supply  on  hand  is  exhausted. 

WEIGHTS  OF  SALUTING  POWDER  CHARGES 


Gun. 


1-pounder  subcaliber 

6-pounder  (2.24-inch)  rapid-fire  gun 

2.95-inch  subcaliber  tube 

3-inch  wrought-iron  gun,  saluting  * .  , 
15-pounder  (3-inch)  rapid-fire  gun.  . 

3-inch  gun  (M.  L.) 

6-pounder  (3. 67-inch),  bronze 

4-inch  rapid-fire  gun 

4.72-inch  rapid-fire  gun,  Armstrong  . , 
5-inch  rapid-fire  gun  (Ord.  Dept.)  .  . , 

6-inch  rapid-fire  gun,  Armstrong 

6-inch  rapid-fire  gun  (Ord.  Dept.) .  . 

8-inch  converted  rifle 

8-inch  smoothbore  gun 

10-inch  smoothbore  gun 

8-inch  rifle 

10-inch  rifle ,  .  . 

12-inch  rifle 

12-inch  mortar. . 


Charge. 


5i  ounces  saluting  powder, 
li  pounds  saluting  powder. 

1  pound  6  ounces  saluting  powder. 

11  pounds  saluting  powder. 

2  pounds  saluting  powder. 

1  pound  mortar  or  saluting  powder. 
1  pound  mortar  or  saluting  powder. 

4  pounds  saluting  powder. 

5  pounds  saluting  powder. 
5  pounds  saluting  powder,  f 
5  pounds  saluting  powder. 
8  pounds  saluting  powder. f 
7  pounds  saluting  powder. 
7  pounds  saluting  powder. 
10  pounds  saluting  powder. 

12  pounds  saluting  powder. f 
18  pounds  saluting  powder. f 
30  pounds  saluting  powder,  f 
18  pounds  saluting  powder. f 


*  This  gun  uses  the  standard  6-pounder  saluting  case, 
t  Used  during  maneuvers  only  if  specially  authorized. 
NOTE. — Smokeless  powder  will  not  be  used  for  blank  charges. 

Blank  metallic  ammunition  should  be  assembled  under  the  personal 
supervision  of  a  commissioned  officer,  who  should  be  held  responsible 
that  tbe  ammunition  is  prepared  and  the  wads  secured  as  prescribed 
above,  and  who  will  mark  the  cartridge  cases  with  his  initials  to  indi- 
cate that  the  round  has  been  assembled  properly,  and  no  blank  metallic 
ammunition  on  which  his  initials  do  not  appear  will  be  used.  Cases 


EXPLOSIVES,   PROJECTILES,   PRIMERS  AND  FUSES  263 

should  be  marked  in  such  manner  that  the  marks  may  be  removed 
after  the  charges  have  been  fired. 

The  primer-inserting  press  issued  is  made  especially  for  the  15- 
pounder  seacoast  gun,  bushings  being  provided  for  guns  of  less  caliber 
using  fixed  ammunition.  Each  post  is  furnished  with  one  of  these 
presses  and  such  bushings  as  may  be  required,  also  decapping  and 
cleaning  outfits. 

Metallic  powder  barrels  of  25  pounds  capacity  or  over  should  be 
returned  to  the  depot  or  arsenal  from  which  shipped;  when  emptied, 
care  should  be  taken  to  store  in  a  dry  place. 

The  table  on  the  opposite  page  shows  the  authorized  weights  of 
blank  charges  used  in  saluting,  etc. 

High  Explosives. — The  high  explosives  are  disruptive,  and  consist 
of  the  shell-fillers,  those  used  in  torpedoes,  mines  and  for  demolition 
purposes.  Those  in  general  use  are:  Gun  cotton,  nitroglycerine,  picric 
acid,  dynamite,  explosive  "D,"  maximite,  trinitrotoluol  and  blasting 
gelatine. 

The  action  of  explosives  of  this  class  is  entirely  different  from 
that  of  those  of  the  low  order.  In  this  case  the  explosion  is  not  con- 
fined to  the  surfaces  of  the  substances  exploded,  but  appears  to  progress 
radially  in  all  directions  throughout  the  mass  from  the  initial  point. 
The  time  is  extremely  short  and  the  effect  is  to  transfer  the  explosive 
from  the  solid  or  liquid  state  to  the  gaseous  state  in  an  almost  inappre- 
ciably brief  interval.  The  gases  are  increased  very  rapidly  in  volume 
and  pressure  by  the  heat  of  the  combination. 

Gun  Cotton. — This  explosive  is  a  nitrocellulose  of  high  nitration 
or  containing  more  than  12.9  per  cent,  of  nitrogen. 

Its  manufacture  is  practically  the  same  as  that  described  for  nitro- 
cellulose powders,  except  that  the  process  is  discontinued  before 
colloidization  takes  place.  When  made  for  military  purposes  the 
purified  pulp  is  taken  from  the  poacher  to  a  stuff  chest  by  suction. 
This  chest  consists  of  a  large  vat  with  an  air-tight  top.  Through  the 
center  of  the  vat  passes  a  vertical  shaft  upon  which  are  mounted  a 
number  of  paddles.  The  purified  pulp  having  been  sucked  up  into 
the  stuff  chest  is  kept  agitated  by  these  paddles  so  that,  the  pulp  will 
be  evenly  distributed  in  suspension  through  the  liquid.  From  the 
stuff  chest  the  pulp  is  drawn  into  the  moulding  press.  This  is  a 
hydraulic  press  made  of  bronze  and  containing  four  moulds.  The 
pulp  is  run  into  these  moulds  and  a  pressure  applied  for  about  four 
minutes.  The  mould  press  blocks  are  then  placed  in  the  mould  of 
the  final  press  and  a  pressure  of  from  6,000  to  7,000  pounds  is  appliedc 


264  THE  SERVICE  OF  COAST  ARTILLERY  % 

While  in  this  press  they  are  stamped  with  the  name  of  the  manufac- 
turer, the  lot  and  the  year. 

The  blocks  from  the  final  press  contain  about  15  per  cent,  water, 
but  before  being  issued  for  storage  they  should  be  soaked  in  pure  water 
until  they  contain  about  25  per  cent,  of  water. 

Gun  cotton  is  recommended  for  use  (when  wet)  for  mines,  torpedoes 
and  demolitions  of  all  kinds.  Its  great  value  as  a  disruptive  agent 
rests  upon  its  great  force  and  in  its  safety  in  manufacture,  storage 
and  handling.  It  is  less  liable  to  accident  or  spontaneous  explosion 
than  any  other  explosive  now  used,  and  when  kept  in  storage  in  a  wet 
state  it  is  non-explosive  except  with  a  powerful  detonator  or  a  small 
piece  of  dry  gun  cotton. 

Cold  has  no  effect  on  dry  gun  cotton.  If  wet  and  exposed  to 
freezing  and  thawing,  the  compressed  cakes  or  disks  will  flake  off  on 
the  surface;  the  -freezing  also  causes  the  mass  of  the  cake  or  disk  to 
open  out  and  be  less  compact.  Variations  of  temperature  between 
32  degrees  and  135  degrees  F.  have  no  effect  on  either  the  physical 
or  chemical  condition  of  gun  cotton.  Even  when  dry  it  is  not  liable 
to  explode  by  a  blow  or  friction  unless  very  closely  confined  and  com- 
pressed. When  wet  in  any  form  it  cannot  be  ignited  by  flame,  and  a 
wet  disk  when  thrown  into  a  fire  will  first  dry  out  on  the  outer  surface 
and  burn  there,  continuing  this  progressively  until  consumed. 

Gun  cotton  when  wet  explodes  more  brusquely  than  when  dry, 
because  the  water  in  the  pores  being  incompressible  increases  the 
velocity  of  the  explosive  wave.  It  has  been  found  by  experiment 
to  detonate  wet  gun  cotton  with  a  dry  priming  charge  of  gun  cotton, 
the  main  charge  and  priming  charge  must  be  in  intimate  contact, 
that  is,  they  must  not  be  separated  by  material  of  any  great  thicknesss. 

Owing  to  its  safety  in  handling  and  storage  it  is  of  great  value  as 
an  explosive  for  submarine  mines  and  is  used  almost  exclusively  for 
that  purpose  when  it  can  be  procured. 

It  is  ordinarily  packed  in  a  wooden  zinc-lined  case,  the  lid  of  which 
has  an  opening  with  a  screw  top,  in  which  water  is  periodically  poured, 
in  order  to  keep  the  charge  thoroughly  saturated  or  up  to  its  wet 
weight.  These  cases  are  weighed  quarterly  and  should  they  be  found 
to  weigh  less  than  their  registered  gross  weight  the  deficiency  is  made 
by  adding  distilled  water. 

Dry  gun  cotton  is  used  as  a  priming  charge  for  submarine  mines  and 
comes  packed  wet  in  glass  jars.  Before  being  used  for  this  purpose  it  is 
necessary  to  dry  the  charge,  in  a  warm  room,  until  weighing  on  two 
successive  days  fails  to  show  any  loss  due  to  evaporation. 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  265 

In  color  gun  cotton  varies  from  white  to  light  yellow  and  is  usually 
issued  in  the  form  of  compressed  cakes  or  that  of  the  pulp  form. 

Nitroglycerine  consists  of  glycerine,  nitric  acid  and  sulphuric  acid. 

The  process  of  manufacture  is  as  follows :  A  large  amount  of  glycerine 
is  nitrated  by  gradually  allowing  a  small  amount  of  glycerine  to  enter 
into  the  presence  of  mixed  acids  in  succession.  The  acids,  which 
consist  of  two  parts  by  weight  of  sulphuric  acid  specific  gravity  1.845, 
to  one  part  of  nitric  acid  specific  gravity  1.150,  are  placed  in  a  lead- 
lined  chamber  above  which  is  a  tank  containing  the  glycerine,  the  two 
being  connected  by  a  pipe  having  a  coil  with  numerous  fine  holes  on 
the  bottom  of  the  acid  chamber.  A  pipe  running  into  the  top  of  the 
glycerine  tank  supplies  compressed  air,  which  forces  the  glycerine  down 
into  the  acids.  If  the  temperature  of  the  acid  chamber  rises  above 
86  degrees  F.  and  cannot  be  controlled  by  stopping  the  admission  of 
glycerine  the  compressed-air  pipes  leading  into  this  chamber  are  opened 
and  the  acid  tanks  cooled  by  the  expansion  of  the  air.  If  the  tempera- 
ture still  rises  the  contents  of  the  chamber  are  drawn  off  into  the  safety 
tanks.  It  requires  about  one  hour  to  charge  the  apparatus,  nitrate 
and  discharge  the  contents.  The  nitroglycerine  should  then  contain 
about  92  parts  of  glycerine  and  189  parts  of  nitric  acid.  When  the  ni- 
tration is  completed  a  cock  is  opened  and  the  contents  are  drawn  off 
by  gravity  into  the  separating  tank. 

The  separating  tank  is  provided  with  a  cock  near  the  top  for  drawing 
off  the  nitroglycerine  into  the  washing  tank  and  three  at  the  bottom  lead- 
ing respectively  to  a  safety  tank,  a  waste  acid  tank  and  a  second  separat- 
ing tank.  It  is  arranged  so  that  the  compressed  air  can  be  admitted  if 
heating  develops,  and  should  this  not  be  effective  the  liquid  can  be 
drawn  off  into  the  safety  tank.  The  nitroglycerine  separating  from  the 
waste  products  rises  to  the  top  and  is  drawn  off  into  the  washing  tank, 
the  waste  products  being  drawn  off  at  the  bottom. 

In  the  washing  tank  the  nitroglycerine  is  kept  under  pure  water, 
compressed  air  being  forced  through  the  liquid  to  keep  the  temperature 
below  86  degrees  F.  In  a  few  minutes  after  the  air  is  shut  off  the 
liquids  separate,  and  the  nitroglycerine,  being  the  heavier,  settles  to  the 
bottom  and  is  drawn  off  through  a  cock  at  the  bottom  of  the  tank. 
The  liquid  is  rewashed  and  then  filtered  to  remove  any  foreign  particles. 
The  final  product  is  allowed  to  stand  in  a  w^arm  room  for  several  days, 
during  which  time  a  small  quantity  of  water  will  arise  to  the  top  and 
may  be  removed  by  skimming  and  absorbing. 

Nitroglycerine  is  made  from  chemically  pure  ingredients,  and  should 
have  the  appearance  of  a  water-white  oily  liquid  without  any  odor. 


266  THE  SERVICE  OF  COAST  ARTILLERY 

Some  commercial  nitroglycerines  have  a  yellow  color,  more* or  less  deep. 
When  free  from  water  it  is  transparent;  the  presence  of  water  makes 
it  milky.  It  has  a  slightly  sweet  taste,  gives  a  burning  sensation,  is 
very  poisonous  and  a  small  quantity  absorbed  through  the  skin,  mouth 
or  nostrils  causes  a  severe  headache,  followed  by  giddiness  and  fainting; 
and,  if  sufficient  quantity  has  been  taken,  produces  rigor  and  uncon- 
sciousness. 

Pure  nitroglycerine  freezes  at  about  4  degrees  C. ,  and  does  not  melt 
from  the  frozen  state  until  about  11  degrees  C.  In  the  frozen  state  it  is 
less  sensitive  to  shock  than  in  liquid  shape  but  the  process  of  thawing 
is  very  dangerous  and  should  never  be  attempted  over  a  naked  flame 
or  by  direct  contact  with  the  heated  metal.  The  only  safe  way  to  thaw 
nitroglycerine  is  in  a  water  bath  the  temperature  of  which  should  never 
be  allowed  to  rise  above  50  degrees  C.  When  frozen,  nitroglycerine  is 
very  liable  to  explode  over  a  naked  flame  or  hot  metal.  Liquid  nitro- 
glycerine is  not  sensitive  to  flame  and  will  extinguish  a  match  plunged 
into  it;  an  incandescent  platinum  wire  will  be  cooled  down,  the  nitro- 
glycerine being  volatilized.  A  small  quantity  of  the  liquid  ignited 
in  the  open  air  will  burn  quietly,  but  if  the  quantity  be  large  and  in, 
any  way  confined  an  explosion  will  be  sure  to  occur.  It  will  explode 
by  a  shock  under  certain  conditions,  as  when  pinched  between  two 
rigid  surfaces  of  metal  or  rock,  and  it  will  be  detonated  if  a  bullet  is 
fired  into  the  mass. 

In  handling  nitroglycerine  rubber  gloves  should  be  used,  and  all 
friction  and  shock  avoided.  As  now  manufactured  it  does  not  deteri- 
orate very  rapidly,  and  if  care  is  taken  to  see  the  vessels  or  crocks  in 
which  it  is  stored  or  transported  do  not  leak  there  should  be  no  danger 
in  handling.  Its  dangerous  qualities  are  due  to  creeping  and  sweating. 
In  storage  liquid  nitroglycerine  is  covered  with  a  layer  of  water.  Its 
chief  value  is  found  in  the  manufacture  of  dynamite,  an  accelerator  for 
smokeless  powders  and  for  blasting  purposes. 

Picric  Acid. — This  is  an  explosive  derived  from  the  nitration  of 
phenol  or  carbolic  acid.  Both  picric  acid  and  its  salts  are  largely  used 
in  detonating  and  disruptive  explosives.  Lyddite,  melinite,  shimose 
powder  and  ecrasite  consist  for  the  most  part  of  picric  acid,  in  fact, 
lyddite  is  simply  melted  picric  acid. 

Picric  acid  has  been  found  by  experiment  to  be  too  sensitive  as  a 
shell  filler  for  armor-piercing  shell,  although  it  has  been  used  success- 
fully as  a  shell  filler  for  field-artillery  projectiles.  Its  process  of  manu- 
facture is  as  follows: 

Equal  quantities  by  weight  of  phenol  and  concentrated  sulphuric 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  267 

acid  are  mixed  in  an  iron  vessel,  stirred  and  heated  by  steam  at  a 
temperature  between  212  and  250  degrees  F.  From  time  to  time  tests 
are  made  to  see  if  the  mixture  formed  is  soluble  in  cold  water.  When 
this  is  so  the  mixture  is  allowed  to  cool  and  twice  the  quantity  of  water 
is  added.  The. nitration  then  takes  place  in  earthen  vessels  standing 
in  running  water  which  can  be  heated  by  steam  pipes.  In  these  re- 
ceivers 3  parts  by  weight  of  nitric  acid  is  placed  and  1  part  of  the 
mixture  described  above,  is  added.  The  latter  is  allowed  to  run  in 
gradually  at  first,  as  the  reaction  is  violent.  Afterwards  it  becomes 
sluggish  and  then  steam  is  turned  on  and  the  temperature  of  the 
solution  raised  to  restore  the  chemical  action. 

The  picric  acid  formed  separates  at  first  into  a  syrupy  liquid,  be- 
coming crystallized  on  cooling.  It  is  separated  from  the  other  liquids 
by  a  centrifugal  machine  and  is  washed  in  the  same  machine  with  pure 
warm  water.  The  crystals  are  further  purified  by  re-dissolving  in  warm 
water,  re-crystallizing  and  finally  drying. 

The  crystals  are  long,  flat  and  lemon-colored.  It  has  a  bitter  taste, 
is  partly  soluble  in  cold  water  but  entirely  so  in  hot  water,  giving  a 
solution  of  a  bright  yellow  color.  It  stains  the  skin  and  is  used  as  a 
yellow  dye.  If  heated  suddenly  it  will  explode,  and  if  added  to  any 
potassium  salt  forms  a  very  sensitive  explosive  and  must  be  handled 
with  great  care.  The  combination  of  picric  acid  with  metal  bases  such 
as  lead,  iron  and  potassium  makes  an  exceedingly  sensitive  compound, 
and  for  this  reason  care  must  be  taken  in  filling  iron  shells  with  picric 
acid  or  its  derivatives. 

Of  all  the  picrates  of  salts  of  picric  acid  there  is  only  one  that  is 
suitable  for  use  as  an  explosive,  and  that  is  ammonium  picrate,  which 
unlike  the  metallic  picrates,  is  insensitive  to  shock. 

Dynamite. — This  term  is  used  in  both  a  general  and  special  sense. 
As  a  general  term  it  includes  all  mixtures  of  nitroglycerine  with  solid 
substances,  in  which  the  latter  hold  the  liquid  nitroglycerine  in  absorp- 
tion. The  solid  substance  is  called  the  base  and  may  be  an  explosive 
or  combustible  material.  In  this  sense  smokeless  powders,  such  as 
cordite,  having  nitroglycerine  as  an  accelerator,  partake  of  the  nature 
of  dynamite,  but  the  name  is  used  with  reference  to  explosives  designed 
for  disruptive  purposes  only. 

In  a  special  sense  the  term  refers  to  the  product  obtained  by  mixing 
liquid  nitroglycerine  with  a  fine,  usually  white,  siliceous  earth  called 
kieselguhr.  This  earth  has  marked  absorbent  properties  due  to  its  cel- 
lular structure,  and  having  once  absorbed  liquid  nitroglycerine  holds  it 
tenaciously.  Kieselguhr  will  absorb  nitroglycerine  to  the  extent  of  over 


268  THE  SERVICE  OF  COAST  ARTILLERY 

80  per  cent,  of  the  weight  of  the  mixture.  The  amount  of  nitroglycerine 
absorbed  in  any  case  determines  the  class  of  dynamite.  That  con- 
taining 75  per  cent.,  the  highest  commercial  percentage,  is  called 
dynamite  No.  1;  50  per  cent,  nitroglycerine,  dynamite  No.  2;  30  per 
cent,  nitroglycerine,  dynamite  No.  3.  In  each  case  of  the  classes  of 
dynamite  mentioned  above  a  little  sodium  carbonate  is  always  added  to 
neutralize  any  free  acid  that  may  be  formed. 

The  commercial  names  for  the  several  classes  of  dynamite  are  as 
follows:  Dynamite  No.  1,  Giant  or  Atlas  powder;  Dynamite  No.  2, 
Atlas  powder  B,  Giant  powder  No.  2,  and  Rendrock;  Dynamite  No.  3, 
Vulcan  and  Judson  powders. 

In  the  manufacture  of  dynamite  the  following  steps  are  taken: 
1.  Kieselguhr  is  converted  into  a  powder  by  the  action  of  heat  in  a 
furnace.  2.  It  is  then  ground  between  rolls,  passed  through  fine 
sieves,  dried  and  packed  in  bags  and  stored  in  a  drying  atmosphere. 
3.  When  the  kieselguhr  is  dried  until  it  contains  not  more  than  5  per 
cent,  of  water  it  is  spread  over  the  bottom  of  a  lead-lined  trough  and 
nitroglycerine  is  pored  over  it  and  mixed  thoroughly.  4.  The  mixture 
is  then  rubbed  through  sieves,  first  through  one  containing  3  meshes  to 
the  inch,  and  then  through  one  containing  7  meshes  to  the  inch.  5.  The 
bulk  dynamite  is  pressed  into  cylinders  about  1  inch  in  diameter  and 
8  inches  long.  These  cylinders  are  called  sticks  or  cartridges,  and  are 
carefully  wrapped  in  paraffine  paper.  Enough  of  the  cartridges  to  weigh 
50  or  100  pounds  are  packed  in  sawdust  in  wooden  boxes.  In  appear- 
ance dynamite  manufactured  in  this  way  has  a  light  brown  to  reddish- 
brown  color  and  resembles  brown  sugar. 

Dynamite  in  the  military  service  is  used  as  a  standard  explosive  for 
submarine  mines  and  in  demolitions.  It  is  more  sensitive  than  gun 
cotton  and  requires  great  care  in  handling  and  storage.  It  is  more 
sensitive  when  thawed  than  in  its  usual  or  frozen  condition. 

Due  to  the  fact  that  it  contains  nitroglycerine,  which  is  one  of  the 
most  sensitive  explosives,  dynamite  can  be  exploded  by  friction  or 
shock.  In  storage,  in  magazines  where  the  temperature  is  apt  to  be 
high  it  will  deteriorate  quite  rapidly,  such  deterioration  being  indi- 
cated by  its  damp,  pasty  condition  or  green  spots  on  the  paraffine 
wrappers.  In  such  cases  care  must  be  taken  not  to  slide  the  boxes  in 
moving.  It  should  also  be  destroyed  in  the  open  air  when  it  has  reached 
this  state  of  deterioration. 

Explosive  "  D  ". — This  explosive  is  a  picric  acid  derivative.  It  is 
a  compound  of  picric  acid  with  certain  other  elements  which  it  has 
been  thought  to  the  best  interests  of  the  service  to  keep  secret.  It  is 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  269 

used  extensively  as  a  shell  filler,  due  to  the  fact  that  it  is  least  sensitive 
to  shock  of  all  the  explosives  considered.  It  is  not  fusible,  that  is, 
it  cannot  be  melted  or  liquefied.  Shells  are  filled  with  it  by  compres- 
sion, that  is,  the  explosive  is  put  in  the  cavity  of  the  shell  in  small 
quantities  and  thoroughly  tamped  with  either  a  copper  or  wooden 
tamper  or  mallet,  until  the  cavity  is  completely  filled. 

The  relative  force  of  explosive  "D"  for  actual  density  of  loading 
as  compared  with  that  of  gun  cotton  is  practically  twice  as  great.  It  is 
perfectly  safe  in  manufacture  and  free  from  very  injurious  effects  on  the 
workmen.  It  is  insensitive  on  impact  and  stands  the  maximum  shock 
of  discharge  safely.  It  is  non-hygroscopic  and  stable  in  storage.  It 
resembles  powdered  sulphur  very  closely  in  appearance. 

Maximite. — This  explosive  is  also  a  picric  acid  compound,  the  com- 
position of  which  has  been  kept  secret.  It  is  fusible  and  a  suitable 
explosive  for  armor-piercing  shell.  It  differs  from  explosive  "D"  in 
that  it  is  melted  when  used  to  fill  shells.  Also  in  the  requirement  that 
the  metal  of  the  shell  must  be  protected  with  rubberine  paint  before  it 
is  put  in.  In  all  other  requirements  as  a  service  shell  filler  it  is  prac- 
tically similar  and  equal  to  explosive  "D." 

It  resembles  explosive  "D"  except  that  it  is  much  darker,  having  a 
light  brown  or  buff  appearance. 

Trinitrotoluol. — This  explosive  is  rapidly  superseding  picric  acid 
as  a  basis  for  shell  fillers.  It  is  slightly  less  powerful  than  picric  acid 
but  possesses  many  advantages  over  it,  one  of  which  is  that  it  will  not 
form  dangerous  combinations  with  other  bodies  with  which  it  may  come 
in  contact,  whereas  picric  acid  in  contact  with  certain  metals  forms  very 
unstable  and  dangerous  picrates.  Trinitrotoluol  is  not  unpleasant  to 
work  with,  nor  does  it  disfigure  like  picric  acid. 

Blasting  Gelatine. — This  is  the  most  powerful  explosive  known. 
It  is  17  per  cent,  greater  in  strength  than  dynamite  No.  1.  It  differs 
from  ordinary  dynamite  in  that  the  usual  pressure  does  not  cause  the 
nitroglycerine  to  exude,  and  it  is  not  affected  by  the  action  of  water 
except  on  the  surface.  The  ingredients  are  nitroglycerine  and  soluble 
nitrocellulose,  about  90  per  cent.,  of  the  former  to  10  per  cent,  of  the 
latter. 

In  manufacture  the  mixing  is  done  in  troughs  at  a  temperature  of 
122  degrees  F.,  with  wooden  spades,  and  when  the  mass  is  so  gelatinized 
as  to  make  it  difficult  to  work  with  spades,  it  is  kneaded  by  hand  like 
bread  dough  until  it  has  a  smooth,  even  consistency.  It  is  then  removed 
and  allowed  to  cool,  when  the  mass  becomes  a  firm,  jelly-like  substance, 
yellow  or  light  brown  in  color,  and  soft  enough  to  be  cut  by  a  knife. 


270  THE  SERVICE  OF  COAST  ARTILLERY 

The  finished  product  is  placed  in  a  machine  very  much  like  an  ordinary 
sausage-making  machine  and  forced  out  in  a  long  cable  and  cut  to  the 
desired  lengths  by  a  bronze  knife.  The  cylindrical  sticks  are  then 
wrapped  with  paraffine  paper. 

The  initial  shock  required  to  detonate  blasting  gelatine  is  six  times 
greater  tnan  that  required  to  detonate  ordinary  dynamite,  and  for  this 
reason  it  is  far  less  sensitive  to  sympathetic  explosion  or  explosion  by 
influence.  When  frozen  it  is  more  sensitive  to  shock  than  dynamite, 
but  freezing  does  not  seem  to  affect  its  explosive  force.  The  same  care 
must  be  exercised  in  thawing  as  in  the  case  of  ordinary  dynamite.  A 
small  quantity  of  it  burns  in  the  open  air  without  exploding  and  it  will 
burn  in  mass  quietly  unless  some  part  reaches  the  exploding  tempera- 
ture, 204  degrees  C.  It  is  very  stable  under  the  action  of  heat,  but  its 
sensitiveness  is  increased  thereby. 

This  explosive  is  far  too  violent  for  many  purposes,  and  it  has 
therefore  been  necessary  to  incorporate  with  the  gelatine  some  suitable 
base,  such  as  sodium  nitrate  and  wood  pulp,  with  a  view  of  regulating 
the  force  of  explosion.  Explosives  of  this  kind  are  called  gelatine 
dynamites  and  consist  of  65  parts  by  weight  of  blasting  gelatine  to 
35  parts  by  weight  of  the  base  described.  It  has  been  found  that  by 
adding  10  per  cent,  of  camphor  to  blasting  gelatine  it  will  not  explode. 
It  cannot  be  used  as  a  shell  filler  and  is  only  suitable  for  purposes  of 
demolition. 

Fulminates. — The  characteristic  feature  of  fulmination  is  that  it  is 
more  brusque  than  in  the  other  two  classes.  The  explosive  blow  is 
not  prolonged  and  it  is  therefore  much  sharper  than  in  the  case  of  other 
explosives.  The  heat  of  the  first  phase  of  the  explosion  is  also  very 
great,  due  to  the  fact  that  the  molecules  of  the  fulminate  are  endothermic, 
that  is,  they  increase  the  temperature,  and  this  in  itself  tends  to  in- 
crease the  sharpness  and  energy  of  the  blow  on  the  initial  molecule. 
Such  a  sharp  molecular  blow  is  thought  to  be  particularly  effective  in 
breaking  up  the  molecular  bonds  of  the  disruptive  class,  and  in  this 
way  an  explosion  of  the  highest  order  is  obtained.  The  abruptness 
of  the  explosion  of  fulminates  and  the  consequent  shortness  of  blow, 
combined  with  the  concentration  of  very  great  heat  at  the  point  of 
ignition,  causes  the  fulminates,  or  as  they  are  frequently  called,  de- 
tonators or  exploders,  to  be  of  great  value  as  originators  of  detonations 
and  explosions  in  the  first  two  classes. 

Exploders  or  Detonators. — The  essential  ingredient  of  all  caps 
and  detonators  is  fulminate  of  mercury,  which  is  formed  from  metallic 
mercury,  nitric  acid  and  alcohol.  The  quantity  of  fulminate  in  any 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  271 

particular  exploder  depends  upon  the  kind  of  explosive  used.  It  may 
require  some  other  ingredient  to  be  mixed  with  the  fulminate,  such  as 
chlorate  or  nitrate  of  potassium,  sulphide  of  antimony,  etc.,  to  give  the 
character  to  the  initial  explosive  blow. 

The  manufacture  of  fulminate  of  m  rcury  is  as  follows:  Equal 
parts  by  weight  of  mercury  and  nitric  acid  (specific  gravity  1.38)  are 
mixed  in  a  glass  carboy.  The  nitric  acid  dissolves  the  mercury  and 
when  completely  dissolved  the  contents  are  allowed  to  cool.  The 
solution  is  then  well  shaken  to  secure  uniformity,  and  emptied  into  a 
second  carboy,  which  contains  10  parts  of  ethyl  alcohol,  and  is  there 
kept  at  a  temperature  of  60  degrees  F.  After  a  few  minutes  the  re- 
action begins,  the  liquid  boils  and  white  vapors  of  nitric  and  acetic 
ether,  carbonic  acid,  etc.  rise  and  pass  off.  The  crystals  of  fulminate 
of  mercury  separate  in  the  form  of  small  gray-colored  needles  in  about 
fifteen  minutes  afterwards.  When  the  reaction  is  completed  the  pro- 
duct is  allowed  to  cool,  it  is  then  filtered  and  washed  with  pure  water 
until  no  trace  of  acid  is  found.  The  fulminate  is  then  placed  in  a 
drying  atmosphere  out  of  the  direct  rays  of  the  sun  and  allowed  to  dry 
until  it  contains  not  more  than  15  per  cent,  of  water. 

The  finished  product  is  usually  made  up  in  packages  containing 
120  grains.  When  packed  it  contains  15  per  cent,  of  water  and  is 
hermetically  sealed  to  prevent  evaporation,  as  it  is  much  more  sensitive 
to  shock  and  friction  in  the  dry  state.  When  it  is  necessary  to  dry  it 
for  use  in  caps  and  detonators  great  care  must  be  exercised.  The  tem- 
perature must  be  kept  below  104  degrees  F.  It  should  not  be  kept  in 
stoppered  bottles  and  especially  not  in  bottles  having  glass  stoppers, 
as  the  friction  of  the  moving  and  inserting  of  the  stopper  might  detonate 
a  particle  of  the  fulminate  caught  in  the  neck  of  the  bottle.  It  is 
exploded  by  a  moderate  blow  of  a  hammer,  by  heat  and  by  friction. 

Fulminate  of  mercury  is  used  very  little  except  in  caps  and  de- 
tonators. Powdered  glass  and  sulphide  of  antimony  are  frequently 
used  with  it  to  increase  its  sensitiveness  to  percussion. 

PROJECTILES 

Projectiles  used  in  seacoast  cannon  are  designed  primarily  to  over- 
come the  resistance  offered  by  armor  plate  to  their  entrance  into  the 
vitals  of  war  vessels,  or  to  carry  a  bursting  charge  into  a  destructive 
radius.  The  power  of  a  projectile  to  accomplish  this  depends  upon  the 
shape  of  the  projectile  upon  impact,  the  possibility  of  its  breaking  up, 
and  the  amount  of  heat  developed  upon  striking  a  plate.  In  the 


272  THE  SERVICE  OF  COAST  ARTILLERY 

manufacture  of  projectiles  it  is  very  difficult  to  make  them  exactly 
alike,  that  is,  exactly  homogeneous.  This  variation  even  extends  to 
projectiles  made  in  the  same  foundry. 

It  is  generally  agreed  that  the  dissipation  of  energy  stored  in  a 
projectile  when  it  strikes  a  target  may  be  accounted  for,  (1)  in  heating 
the  target;  (2)  in  heating  the  projectile;  (3)  in  changing  the  form  of 
the  projectile;  (4)  in  changing  the  form  of  the  target.  From  the 
standpoint  of  results  obtained,  all  but  the  last  of  these  are  a  waste. 

The  amount  of  energy  in  the  projectile  which,  upon  impact  takes 
the  form  of  heat,  can  be  approximately  estimated.  It  has  been  found 
that  the  temperature  upon  impact  is  sufficiently  great  to  ignite  a  bursting 
charge  of  black  powder  which  requires  a  heat  of  540  degrees  F.  Again 
a  bright  red  spot,  even  on  bright  days,  can  be  observed  at  the  instant 
the  projectile  strikes  the  plate,  which  shows  that  the  plate  in  the  im- 
mediate vicinity  of  the  impact  is  heated  to  a  high  degree  of  temperature. 

The  penetrative  effect  of  a  projectile  depends  upon,  (1)  its  shape; 
(2)  its  material;  (3)  its  energy  and  diameter;  (4)  the  angle  at  which 
it  strikes  the  target;  (5)  whether  it  is  capped  or  uncapped. 

The  shape  believed  to  accomplish  the  best  results  is  that  of  a 
cylindrical  body  with  ogival  head,  the  latter  having  a  radius  of  from 
two  to  two  and  one-half  calibers,  that  is,  the  radius  of  the  curve  forming 
the  head  is  drawn  from  the  arc  of  a  circle  the  diameter  of  which  is  from 
two  to  two  and  one-half  times  the  diameter  of  the  projectile. 

The  material  best  suited  for  projectiles  designed  to  pierce  armor  is 
that  which  will  neither  break  up  on  impact  nor  change  its  shape. 
Forged  oil-tempered  steel  of  special  treatment  and  composition  has 
been  found  to  come  nearest  to  fulfilling  these  conditions. 

The  energy  of  a  projectile  necessarily  depends  upon  its  weight  which, 
for  any  given  projectile,  is  a  function  of  its  diameter.  The  best  weight 
for  a  projectile  of  given  diameter  is  generally  found  by  obtaining  the 

value  of  the  ratio  — ,  in  which  w  is  the  weight  of  the  projectile  and  d 
a3 

the  diameter. 

The  smallest  angle  of  impact  (measured  from  the  surface  of  the  plate) , 
at  which  a  projectile  will  hold  or  bite,  is  called  the  biting  angle.  See 
Fig.  8.  For  plates  of  different  materials,  this  angle  changes.  For 
plates  of  comparatively  soft  material,  such  as  wrought  iron  and  low 
steel,  or  if  the  plate  is  overmatched,  the  shot  will  bite  at  a  slightly  less 
angle  than  in  the  case  of  face-hardened  steel,  owing  to  the  fact  that  the 
plate  bends  slightly  on  impact.  For  face-hardened  armor  the  biting 
angle  cannot  be  mathematically  seated.  As  a  general  rule  it  may  be 


PLATE   XIX 


Types  of 

1.  Friction  Primer,  Axial  Vent. 

2.  Friction  Primer,  Radial  Vent. 

3.  Friction  Primer,  Sub.  Cal.  Firing. 

4.  Obturating  Friction,  Old  Model  Vent. 

5.  Obturating  Friction,  Siege,  New  Vent. 

6.  Drill  Primer,  Old  Model  Vent. 

7.  Drill  Primer,  New  Model  Vent. 

8.  Electric  Primer,  Axial  and  Radial  Vent. 

9.  Obturating  Electric,  Old  Model  Vent. 

10.  Electric    Primer   for   use    with    Armstrong 
Adapter. 


Primers. 

11.  Combination    Electric    and    Friction,  New 
Vent. 

12.  Percussion  for  use  with  Armstrong  Adapter. 

13.  110-Grain  Percussion  Primer. 

14.  20-Grain  Percussion  Primer. 

15.  Percussion  Primer,  Battery  Cup. 

16.  20-Grain  Saluting  Primer. 

17.  Igniting  Primer. 

18.  20-Grain  Igniting  Primer. 

19.  110-Grain  Igniting  Primer. 


OF    THE 

UNIVERSITY 

OF 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  273 

defined  as  that  angle  at  which  the  component  of  the  energy  of  the 
projectile,  normal  to  the  plate,  is- sufficient  to  smash  in  the  hard  face, 
the  projectile  at  the  same  time  holding  together  long  enough  to  penetrate. 
A  projectile  has  its  greatest  penetration  at  normal  impact  and  its 
penetrative  power  decreases  as  the  angle  of  impact  increases,  but  not 
in  exact  proportion. 

All  armor-piercing  projectiles  are  now  fitted  with  soft  steel  caps, 
which,  under  favorable  angles  of  impact,  increase  their  penetrative 
effect  when  attacking  hard-faced  armor.  The  cap  as  adapted  in  the 
service  consists  of  a  cylindrical  piece  of  soft  steel  about  half  a  'caliber 
of  the  projectile  in  diameter,  bored  out  to  a  depth  of  about  two-thirds 
of  its  length  to  fit  over  the  nose  or  point  of  the  projectile.  It  weighs 


FIG.  21. — Armor  Plate  after  Attack  by  Capped  and  Uncapped  Projectiles, 
ordinarily  about  2^  to  5  per  cent,  of  the  weight  of  the  projectile. 
A  recess  or  cavity  in  the  interior,  that  is,  between  the  nose 
of  the  projectile  and  the  cap  when  assembled,  contains  a  lubricant, 
usually  graphite.  The  cap  is  made  fast  by  a  small  cylindrical  groove  cut 
in  the  nose  of  the  projectile,  the  cap  being  forced  on  under  pressure. 
In  the  case  of  cast-iron  projectiles  used  in  tests  and  practice,  the  nose 
is  cut  off,  the  head  bored  to  receive  a  threaded  portion  of  the  cap  which 
is  screwed  into  place,  the  object  being  to  make  the  practice  projectile 
identical  in  weight  and  shape  to  those  used  in  service. 

The  theory  of  the  action  of  the  cap,  which  seems  most  reasonable, 
is  that  when  the  mass  consisting  of  the  projectile  and  cap  meets  the  hard 
face  of  the  plate,  the  latter  acts  as  a  buffer  against  the  hard  and  im- 
penetrable surface,  and  elastically  dishes  the  plate  on  impact.  The 
cap  is  strong  enough  to  transmit  the  stress  of  impact,  and  at  the  same 
time  the  projectile  proper  is  not  stopped  as  suddenly  as  in  the  case  of 


274  THE  SERVICE  OF  COAST  ARTILLERY 

one  not  capped,  but  continues  to  advance  through  the  cap,  which,  being 
soft,  is  comparatively  easy  and  when  the  point  reaches  the  plate  it 
finds  the  latter  already  dished  practically  to  its  elastic  limit.  Again, 
it  gives  the  projectile  a  most  decided  advantage  in  having  the  tendency 
of  preventing  the  projectile  from  breaking  up  on  impact. 

Fig.  21  is  a  photographic  view  of  a  6-inch  cemented  armor  plate 
against  which  were  fired  two  shots  from  a  6-inch  gun,  at  practically 
the  same  velocity.  The  projectiles  in  both  cases  were  alike,  excepting 
that  the  first  was  uncapped  while  the  other  was  capped,  similar  to  that 
shown  in  the  view.  The  striking  energies  were  virtually  the  same; 
but  the  uncapped  projectile  failed  to  penetrate  and  broke  up  on  impact, 
the  nose  remaining  embedded  in  the  plate.  The  capped  projectile,, 
on  the  other  hand,  made  a  clean  hole  through  the  plate  and  was  recovered 
whole,  with  the  exception  of  a  small  piece  broken  from  the  point  as 
shown  in  the  illustration. 

In  the  matter  of  acceleration  of  penetration,  for  normal  impact 
against  cemented  plate,  with  velocities  exceeding  1,800  f.  s.,  the  use 
of  the  cap  will  add  about  one-sixth  to  the  penetrative  power  of  the 
projectile;  at  angles  of  impact  greater  than  30  degrees  the  advantage 
gained  by  the  cap  is  nil  or  almost  so;  with  velocities  less  than  1,800 
f.  s.,  the  cap  is  practically  useless.  Recently  tests  have  been  made 
with  a  new  form  of  cap,  and  good  results  obtained.  This  cap  is 
more  pointed  and  covers  the  entire  ogive,  which  has  given  rise  to  the 
term  "  long  nose"  to  projectiles  so  capped. 

SERVICE  PROJECTILES 

Armor-Piercing  Shot  are  made  of  forged  steel  with  a  small  cavity 
designed  primarily  to  facilitate  the  tempering  and  hardening  process. 
The  cavity  may  be  filled  with  a  "shell  filler"  consisting  of  a  high 
explosive  bursting-charge.  They  are  armed  with  a  delayed  action 
fuse,  thus  permitting  of  the  perforation  of  armor  plate  before  the  bursting 
charge  is  ignited.  (See  Fig.  22). 

Armor-Piercing  Shell  are  made  of  forged  or  cast-steel  with  a 
larger  cavity  than  that  of  shot.  They  are  designed  to  carry  a  large 
bursting-charge  of  high  explosive  and  to  attack  the  thinner  side  armor 
of  battleships  or  the  vertical  armor  of  cruisers.  They  are  also  provided 
with  a  delayed  action  fuse. 

Deck-Piercing  Shell  are  made  of  forged  or  cast-steel  with  a  cavity 
of  about  the  same  dimensions  as  armor-piercing  shell.  They  are 
provided  with  a  torpedo  detonating  pierce  fuse. 


l?/rKr>  mortar  she//.  Torpedo,  forged  step/. 


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276  THE  SERVICE  OF  COAST  ARTILLERY 

Cast-iron  Shot  are  used  exclusively  for  tests  and  service  target 
practice.  Their  weight  and  dimensions  are  identical  with  the  armor- 
piercing  shot. 

Torpedo  Shell  are  made  of  forged  steel  and  are  designed  to  carry  a 
very  large  bursting  charge  of  high  explosive  onto  the  decks  of  war 
vessels.  They  weigh  either  800  or  1000  pounds,  and  are  provided 
with  a  major-caliber  base  detonating  fuse. 

The  table  on  opposite  page  gives  the  weights  of  projectiles  and  their 
armor  piercing  capacity: 

PAINTS  FOR  PROJECTILES 

To  distinguish  the  character  of  metal  of  which  projectiles  are  made 
and  their  armor-piercing  qualities,  as  well  as  the  position  and  nature 
of  their  bursting-charge,  conventional  colors  are  prescribed  for  use  on 
the  exterior.     The  body  color  of  all  projectiles  is  black. 
Colors  to  Distinguish  the  Character  of  Metal. 

Forged  or  Wrought  Steel — Blue  gray. 

Cast-Steel — Warm  gray. 

Cast-Iron — Olive  green. 

Chilled  Iron — Light  green. 

Brass — Light  yellow. 

Copper — Light  reddish  brown. 

The  colors  above  named  are  also  used  to  indicate  the  degree  of  armor- 
piercing  quality  of  the  projectile,  as  well  as  the  position  of  its  center  of 
gravity,  the  latter  being  essential  to  facilitate  the  raising  and  lowering 
of  projectiles  with  shot  tongs. 

To  indicate  the  degree  of  armor-piercing  quality,  a  greater  or  less 
portion  of  the  head  is  painted  with  the  color  corresponding  to  the 
metal.  The  band  indicating  the  center  of  gravity  is  also  of  the  color 
corresponding  to  the  metal.  It  is  one-half  caliber  wide  and  extends 
equally  above  and  below  the  position  of  the  center  of  gravity.  It  may 
also  be  employed  with  the  smaller  calibers  of  projectiles  to  indicate 
the  character  of  the  metal. 

Colors  to  Distinguish  the  Character  of  the  Bursting  Charge. 

Gun  cotton — White. 

Explosive  "D"  or  Dunnite— Deep  (chrome)  yellow. 

Maximite — Dark  buff. 

Rifle  or  Charcoal  Powder — Vermilion. 

The  bursting-charge  color  is  applied  to  the  base  and  the  cylindrical 
portion  of  the  body  in  rear  of  the  copper  rotating  band.  Until  the 
projectile  is  filled,  these  portions  may  remain  black. 


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278  THE  SERVICE  OF  COAST  ARTILLERY 

On  Armor-Piercing  Shot,  the  whole  head,  including  the  soft-metal 
cap,  and  the  center  of  gravity  band,  is  painted  blue  gray.  The  charge 
color  appears  as  stated  above,  if  the  projectile  is  a  cored  shot. 

On  Armor-Piercing  or  Deck-Piercing  Shell,  one-half  of  the  head, 
measured  from  the  point;  and  the  center  of  gravity  band,  is  painted 
blue  gray.  The  charge  color  appears  as  stated  above. 

On  Chilled-Iron  Shot,  one-half  of  the  head,  measured  from  the 
point;  and  the  center  of  gravity  band,  is  painted  light  green.  The 
charge  color  appears  as  stated  above,  if  the  projectile  is  a  cored  shot. 

On  Cast-iron  Shot,  the  center  of  gravity  band  is  painted  olive   green 

On  Torpedo  Shell,  the  center  of  gravity  band  is  painted  blue  gray. 
The  charge  color  appears  as  stated  above. 

On  Shrapnel,  the  entire  body  is  painted  black,  with  a  band  of 
vermilion  on  the  head  below  the  fuse  to  indicate  a  front  charge,  or  on 
the  cylindrical  portion  of  the  body  in  rear  of  the  copper  rotating  band 
to  indicate  a  base  charge.  Those  used  for  fixed  ammunition  are 
painted  all  black  above  the  copper  band. 

On  cannister,  the  entire  body  is  painted  black. 

Before  the  paint  is  applied  the  surfaces  should  be  cleaned  and  all 
grease  or  oil  removed.  It  should  be  applied  by  brush  and  rubbed  on 
evenly,  particularly  on  parts  required  to  fit  the  bore  closely.  Care  is 
necessary  that  the  junction  of  two  colors  does  not  overlap  to  produce 
inequalities  of  thickness.  ,The  thickness  of  the  coating  generally  must 
be  limited  to  the  least  amount  required  to  produce  the  color. 

The  cavities  of  cored  shot,  shell  and  shrapnel  made  to  contain  a 
bursting-charge  of  powder  are  coated  with  "Turpentine  Asphaltum 
Varnish,  best  quality."  The  process  consists  of  thoroughly  cleaning 
the  cavity  of  all  greasy  matter  and  pouring  in  the  liquid,  then  rolling 
and  turning  the  projectile  to  insure  even  distribution,  and  pouring  out 
the  excess.  The  projectile  is  then  allowed  to  stand  with  the  fuse  hole 
down  for  a  time  sufficient  to  insure  thorough  draining  of  excess.  The 
residue  from  fuse  threads  is  removed  by  means  of  a  cloth  soaked  in 
benzene  and  a  tap.  The  fuse  hole  is  left  open  for  the  circulation  of  air 
until  after  the  coating  has  hardened. 

The  "body"  of  coating  can  be  increased  by  a  second  coating  after 
the  first  has  dried,  or  by  thickening  the  varnish,  through  evaporation, 
before  applying. 

Cored  shot  or  shell  which  are  charged  with  picric  acid  compounds 
are  first  coated  on  the  interior  with  paraffin  or  rubberine  paint  No.  2, 
the  process  consisting  of  melting  the  wax  and  pouring  it  in  as  described. 

The  object  of  these  coatings  is  to  prevent  the  generation  of  the 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  279 

sensitive  qualities  produced  in  some  explosives  when  exposed  to  iron 
or  steel,  such  qualities  causing  them  to  detonate  from  the  slightest 
friction. 

PRIMERS 
(See  Plate  XIX) 

Primers  are  devices  used  to  ignite  powder  charges  in  guns.  They 
are  classed,  according  to  the  method  by  which  the  ignition  is  produced, 
into  friction  primers,  electric  primers,  percussion  primers  and  igniting 
primers.  There  is  also  a  combination  primer  so  constructed  that  it 
may  be  fired  by  either  of  the  two  methods  named  above.  Primers 
known  as  obturating  primers,  in  addition  to  affording  a  means  of 
igniting  a  charge,  also  act  as  a  gas  check  and  prevent  the  escape  of 
powder  gases  through  the  vent  by  closing  it. 

Friction  Primers. — Primers  of  this  class  consist  of  those  exploded 
by  frictional  heat;  they  are  composed  essentially  of  a  body  of  brass  or 
Tobin  bronze;  a  friction  pellet,  composed  of  a  mixture  of  sulphide 
of  antimony;  chlorate  of  potash;  sulphur;  ground  glass;  and  usually 
a  matrix,  used  to  hold  the  other  parts  together,  such  as  beeswax  or 
tar;  a  toothed  or  serrated  wire,  to  ignite  the  friction  pellet  by  fric- 
tional heat  when  forced  through  it;  and  the  priming  charge  of  blac  : 
powder.  It  is  essential  that  there  shall  be  no  escape  of  gas,  either 
through  or  around  the  primer  body  on  discharge,  especially  in  case  of 
high-power  guns,  therefore  most  of  the  primers  of  this  class,  especially 
those  used  in  seacoast  cannon,  are  made  obturating.  The  friction 
primers  in  use  are  the  obturating  friction  primer  for  siege  and  sea- 
coast  cannon  shown  in  Fig.  23.  The  primer  illustrated  in  Fig.  23 
was  designed  for  use  with  old-model  vents  and  are  gradually  being 
replaced  in  the  service  by  the  primers  for  the  new-model  vent  shown  in 
Fig.  29,  which  is  commonly  known  as  the  button  primer. 

In  addition  to  the  friction  primers  above  described,  the  primer 
shown  in  Fig.  24 ;  known  as  the  drill  primer  for  new-model  vents,  has 
been  designed  to  take  the  place  of  the  relatively  expensive  combination 
electric-friction  primer  for  use  in  drill,  saluting  and  subcaliber  practice. 
The  method  of  operation  of  the  friction  primer  consists  in  pulling  the 
serrated  end  of  the  copper  wire  through  the  friction  composition.  The 
pull  on  the  lanyard  draws  the  serrated  wire  through  the  friction  com- 
position and  ignites  it;  the  flame  communicates  to  the  rifle  powder  and 
thence  through  the  vent  to  the  powder  charge  in  the  gun. 

The  lanyard  should  be  pulled  from  a  position  as  near  to  the  rear  of 
the  gun  as  possible.  A  strong,  steady  pull  from  one  man  with  as  short 


280 


THE  SERVICE  OF  COAST  ARTILLERY 


BODY (BRASS) 

SAFETY  BLOCK  (BRASS) 

SERRATED  WIRE  (BRASS) 


GAS  CHECK  (BRASS) 

PAPER  CYLINDER 
FRICTION  COMPOSITION 
PRIMER  CHARGE 
LOOSE  RIFLE  POWDER 

•PRIMER  CHARGE 
CLOSING  CUP (BRASS) 

FIG.  23. 


•REAR  WIRE  (BRASS) 


(BRASS) 
SERRATED  WIRE  (BRASS) 

-GAS  CHECK (BRASS) 
•PAPER  CYLINDER 

—FRICTION  COMPOSITION 

PRIMER  CHARGE 
LOOSE  RIFLE  POWDER 

CLOSING  CUP (BRASS) 

FIG.  24. 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES 


281 


a  lanyard  as  practicable  should  be  used.  Where  a  long  lanyard  is  used, 
the  slack  causes  the  force  to  be  applied  slowly,  increasing  the  chances 
for  a  misfire. 

If  a  primer  cannot  be  fired  by  one  man,  it  should  be  rejected  and 
another  used.  Two  men  pulling  on  a  lanyard  will  injure  the  firing 
mechanism,  in  case  one  is  used.  When  a  primer  is  pulled  and  fails 
to  fire  it  should  be  removed  from  the  vent ;  the  wire  should  immediately 
be  bent  around  the  primer  through  an  angle  of  180  degrees  to  prevent 
it  from  being  used  again. 

The  obturating  friction  primer  for  new-model  vent  shown  in  Fig.  25, 
was  designed  to  increase  the  rapidity  of  fire  of  all  guns,  as  it  is  more 
readily  inserted  in  the  gun  and  after  use  more  easily  taken  out  of  the 
vent.  In  order  to  use  a  primer  of  this  kind  it  became  necessary  to  add 

BUTTON  (BRASS) 
WIRE  (BRASS) 


BODYCTOBIN  BRONZE) 

SERRATED  CYLINDER 
'&  GAS  CHECK 
'VULCANITE  WASHER 
-FRICTION  COMPOUND 
T  r"p  T  nw 

°   N 


(BRASS) 

PRIMER  CHARGE  .THREE 
'CYLINDERS  (20  GR.lf 
^LOOSE  RIFLE  POWDER 
•PRIMER  CHARGE  CONTD. 
END  CLOSING  CUP 

FIG.  25. 

a  new  firing  mechanism  to  the  breechblocks  of  the  guns  in  which  it  is 
used.  The  head  of  the  primer  is  firmly  held  by  the  firing  mechanism, 
so  that  the  primer  cannot  be  blown  out  at  the  discharge  of  the  piece. 
The  firing  wire  is  engaged  and  pulled  by  a  slotted  lever  actuated  by  the 
pull  on  the  lanyard. 

This  primer  consists  of  a  brass  body  with  a  brass  firing  wire  passing 
loosely  through  the  hole  in  the  serrated  cylinder,  the  end  of  the  wire 
being  flush  with  the  end  of  the  cylinder  when  the  nut  on  the  wire  bears 
against  the  interior  shoulder.  The  friction  composition,  pressed  into 
the  brass  case,  surrounds  the  cylinder  above  the  serrations.  A  vul- 
canite washer  holds  the  friction  composition  in  place  and  prevents  it 
from  crumbling  when  the  pull  is  applied.  The  nut  screwed  to  a  bearing 


282  THE  SERVICE  OF  COAST  ARTILLERY 

on  the  case  holds  the  assembled  parts  in  place.  Three  holes  through 
the  nut  permit  the  passage  of  the  flame  from  the  friction  composition 
to  the  priming  charge  of  powder. 

The  action  of  the  primer  is  as  follows:  When  the  wire  is  pulled, 
ignition  of  the  friction  composition  is  effected.  The  conical  end  of  the 
cylinder  is  pulled  to  its  seat  in  the  body  of  the  primer,  and  prevents 
escape  of  gas  to  the  rear. 

One  of  the  late  improvements  in  this  primer  is  its  arrangement  by 
which  the  wire  may  be  moved  forward  without  carrying  the  cylinder 
and  the  friction  composition  with  it,  and  therefore  without  danger  of 
firing  the  primer  in  case  the  wire  is  pushed  back  after  a  primer  has  been 
taken  from  a  vent  in  case  of  a  misfire.  In  the  earlier  models  the  teeth 
were  formed  on  the  wire,  and  it  was  found  when  a  primer  had  failed 
to  fire  it  might  be  fired  accidentally  in  case  the  wire  was  pushed  back. 

Drill  Primer. — This  primer  is  shown  in  Fig.  24.  It  is  constructed 
practically  the  same  as  the  primer  just  described  except  that  its  parts 
are  more  cheaply  made.  It  is  the  only  primer  issued  unassembled. 
The  button  wire,  body,  serrated  wire,  cylinder  of  smokeless  powder 
and  friction  composition  are  furnished  separately.  The  rifle  powder, 
closing  caps  and  necessary  assembling  tools  are  furnished  for  assembling 
and  disassembling  the  drill  primers. 

The  serrated  wire  with  the  friction  composition  is  first  inserted  in 
its  seat  in  the  body  and  the  button  wire  screwed  on  the  end.  The  body 
is  then  filled  with  25  grains  of  loose  rifle  powder  and  the  end  closed 
with  the  brass  cap.  To  prevent  the  displacement  of  the  cap,  the  end 
of  the  primer  is  sealed  with  a  composition  furnished  for  that  purpose. 

Drill  primer  cases  are  intended  to  be  reloaded  as  many  times  as 
possible,  and  for  this  purpose  the  drill  primer  kit  consists  of  30  primer 
cases,  30  button  wires,  friction  pellets,  closing  caps,  loading  tools  and 
a  resizing  die  for  priming  cases.  The  drill  primer  costs  approxi- 
mately five  cents,  and  with  proper  care  a  drill  primer  case  will  stand 
about  ten  firings  before  becoming  unfit  for  further  use.  To  preserve 
the  cases  they  should  be  carefully  cleansed  with  a  hot  solution  of  lye 
immediately  after  firing,  and  thoroughly  dried  before  being  put  away. 
The  resizing  die  is  used  for  the  purpose  of  readjusting  the  shape  of  the 
primer  cases  that  have  become  swollen  or  bent  out  of  shape. 

Electric  Primers. — Primers  of  this  class  consist  of  those  exploded 
by  an  electric  wire  heated  to  incandescency.  The  service  electric 
primer  consists  essentially  of  the  primer  body,  the  lead  wire  or  wires,  the 
platinum  wire  bridge,  the  gun  cotton  primer  charge,  the  primer  charge 
proper  and  the  insulating  parts.  The  essentials  of  an  electric  primer 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES 


283 


are  that  it  should  be  simple  in  construction,  thoroughly  free  from  short 
circuits,  sure  in  its  action  when  the  proper  current  is  applied,  uniform 
as  to  the  firing  current,  and  so  constructed  that  the  obturation  of  the 
gas  is  complete  through  and  around  the  primer  body.  The  amount  of 
current  usually  required  to  fire  an  electric  primer  is,  under  ordinary 
conditions,  75/100  of  an  ampere.  The  electric  primer  for  axial  and 
radial  vents  is  shown  in  Fig.  26,  and  consists  of  the  parts  indicated 
thereon.  It  is  the  only  two-wire  electric  primer  found  in  the  service. 
The  circuit  between  the  two  wires  is  completed  across  the  platinum 


-INSULATED  WIRE 
(COPPER) 


SLEEVE (COPPER) 
CARTRIDGE 

STEM  WRAPPING 
HARDWOOD  PLUG 
GUN  COTTON 
WIRE  BRIDGE 
(PLATINUM) 
PRIMER   CHARGE 

(BLACK  POWDER) 
STEM(COPPER) 


BEES  WAX 
AND  TAR 

FIG.  26. 


GUN 

COTTON 

IGNITING 
PELLETS 

CLOSING 
CUP 


INSULATED  WIRE 

VULCANITE  BUSHING 
BODY(TOBIN  BRONZE) 


VULCANITE  WASHER 
LEATHER  WAS 
CONTACT  PLUG 
INSULATING  C 
PLATINUM  WIRE  BRIDGE 
CONTACT  CUP(BRASS) 
CLOSING  SCREW( BRASS) 
PAPER  WASHER 
IGNITING  POWDER 


FIG.  27. 


bridge  and  the  electric  current  passing  over  the  circuit  heats  the  wire, 
igniting  the  gun  cotton  surrounding  the  bridge,  which  in  turn  ignites 
the  primer  charge. 

The  electric  primer  for  siege  and  seacoast  cannon  with  old  model 
vents  is  shown  in  Fig.  27,  and  is  used  generally  in  the  same  cannon  as 
the  obturating  friction  primer  shown  in  Fig.  23.  The  principal  parts 
are  indicated  on  the  cut.  The  copper  wire,  insulated  throughout  its 
entire  length  in  the  primer  body,  is  threaded  to  the  brass  contact  plug. 
After  these  two  parts  are  assembled,  the  metal  of  the  contact  plug  is 


284 


THE  SERVICE  OF  COAST  ARTILLERY 


crimped  in  around  the  wire  to  prevent  accidental  unscrewing.  The 
vulcanite  washer,  the  lead  washer,  and  the  insulating  cylinder,  insulate 
the  contact  plug  from  the  primer  body.  The  front  end  of  the  contact 
plug  fits  into  the  counterbore  in  the  rear  end  of  the  vulcanite  insulating 
cylinder.  The  front  end  of  the  vulcanite  insulating  cylinder  is  counter- 
bored  to  the  contact  cup,  which  is  bored  centrally  to  the  hole  leading  to 
the  primer  cavity.  The  interior  of  the  primer  body  is  threaded  as 
shown  for  the  closing  screw.  Both  the  contact  plug  and  the  contact 
cup  extend  beyond  the  ends  of  the  insulating  cylinder,  so  that  when  the 
closing  screw  is  set  up  tight  all  the  interior  parts  referred  to  are  held 
firmly  together. 


NTAC' 


CUP  (BR 
ING  CYLIJ 
INSULATING  PLUG 
CONTACT  PLUG  (BRASS) 
PLATINUM  WIRE  BRIDGE 
GUN  COTTON  IGNITER 


PRIMER  CHARGE 


END  CLOSING  DISK 
(CARD  BOARD) 

FIG.  28. 


A  platinum  wire  bridge  of  2/1000  of  an  inch  in  thickness  is  soldered 
to  the  front  end  of  the  contact  plug  to  the  contact  cup.  The  electrical 
connection  of  the  primer  body  is  secured  through  the  threads  of  the 
closing  screw.  The  platinum  wire  bridge  is  surrounded  with  a  small 
priming  charge  of  dry  gun  cotton,  so  that  when  the  bridge  is  heated 
by  the  passage  of  the  electric  current  the  gun  cotton  is  ignited,  which 
in  turn  ignites  the  pellets.  These  pellets  are  composed  of  21  grains 
of  compressed  black  powder.  On  the  discharge,  the  pressure  of  the  gas 
forces  the  contact  plug  against  the  washers  and  also  forces  the  thin  walls 
of  the  primer  out  against  the  primer  seat,  thus  producing  an  effective 
gas  check. 

The  110-grain  electric  primer  shown  in  Fig.  28  is  designed  for  use  "in 
all  guns  employing  metallic  ammunition,  and  equipped  with  electric 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES 


235 


firing  attachments,  such  as  the  3-inch  R.  F.  gun,  model  of  1902,  and  all 
of  the  Armstrong  seacoast  guns  in  the  service.  The  parts  are  indicated 
in  detail  in  the  cut.  The  electric  element  of  the  primer  consists  of  a 
wire  bridge  soldered  to  the  contact  disk,  which  is  then  pressed  to  the 
bottom  of  the  contact  cup;  the  contact  cup  is  then  pressed  into  the 
insulating  cylinder,  in  which  it  is  made  a  snug  fit;  a  small  quantity  of 
gun  cotton  is  placed  around  the  bridge,  after  which  the  insulating  plug 
is  assembled  in  the  open  end  of  the  contact  cup.  The  contact  plug, 
which  is  centrally  bored  for  the  passage  of  the  flame,  and  the  platinum 
bridge  is  assembled  with  the  boss  or  projection  fitting  into  the  end  of  the 

BUTTON  (BRASS) 
WIRE  (BRASS) 


SUPPORT 

FOR  BRIDGE 
GUN  COTTON 

LOOSE  POWDER- 


INSULATING 
CYLINDER 


(PAPER) 
SS) 


BODY  (TOBIN  BRONZE) 
SERRATED  CYLINDER 
AND  GAS  CHECK 

,  WASHER  (VULCANITE) 
FRICTION  COMPOSITION 
CASE  FOR  FRICTION 

COMPOSITION 
(PLATINUM  WIRE  BRIDGE 
CONTACT  NUT 

?  (VULCANITE) 
COMPRESSED  POWDER 
•E1ID  CLOSING  CUP  (BRASS) 

FIG.  29. 


insulating  plug,  the  bridge  passing  out  through  the  central  hole  and 
being  soldered  into  a  groove  in  the  surface  of  the  contact  plug. 

The  diaphragm  separating  the  recess  for  the  electric  element  from 
the  black  powder^  cavity  is  centrally  bored  to  permit  ready  passage  of 
the  flame  from  the  gun-cotton  igniter  when  the  primer  is  fired. 

Combination  Electric  Friction  Primer. — Primers  of  this  class  consist 
of  those  which  can  be  exploded  by  either  a  frictional  heat  or  by  an 
electric  wire  heated  to  incandescency,  or  both.  The  primer  shown  in 
Fig.  29,  known  as  the  combination  electric  and  fricting  primer  (button 
primer)  has  been  adopted  for  use  in  seacoast  cannon  provided  with 


286  THE  SERVICE  OF  COAST  ARTILLERY 

new  model  vents  and  will  eventually  be  used  in  all  seacoast  cannon 
except  those  provided  with  percussion  firing  ammunition.  Its  great 
advantage  is  that  it  is  readily  inserted  and  removed  from  its  seat. 
It  provides  two  methods  of  firing  and  permits  greater  rapidity  of  fire. 
Its  essential  parts  are  marked  in  detail  in  the  figure. 

The  friction  composition  of  this  primer  consists  of  the  following 
ingredients:  50  parts  by  weight  of  chlorate  of  potash,  27  parts  by 
weight  of  sulphide  of  antimony,  10  parts  by  weight  of  sulphur  and  13 
parts  by  weight  of  ground  glass.  No  matrix  is  used  with  the  com- 
position, the  ingredients  being  thoroughly  incorporated  and  inserted 
as  a  finely  pulverized  powder  into  the  case  and  pressed  into  a  solid 
pellet  which  surrounds  the  cylindrical  part  of  the  serrated  cylinder 
so  that  the  teeth  of  the  latter  are  not  imbedded  in  the  composition 
but  rest  on  the  compressed  pellet. 

The  electric  element  consists  of  a  paper  cylinder  which  surrounds 
the  wire  insulating  it  from  the  firing  mechanism,  the  insulating  plug 
insulates  it  from  the  primer  body.  The  friction  composition  pellet, 
which  is  a  non-conductor  of  electricity,  insulates  the  serrated  cylinder, 
which  is  electrically  connected  with  the  wire  from  the  walls  of  the 
primer  body.  The  support  for  the  platinum  wire  bridge,  when  the 
primer  is  assembled  by  screwing  the  closing  screw  into  the  front  end 
of  the  case,  presses  tightly  against  the  end  of  the  wire,  making  the  elec- 
trical connection  at  this  point.  The  vulcanite  cap  insulates  the  prongs 
of  the  support  from  the  closing  screw.  The  platinum  wire  bridge  is 
soldered  to  the  support  and  to  the  closing  screw.  The  case,  into  the 
front  of  which  the  screw  is  threaded,  screws  into  the  primer  body  as 
shown  on  the  drawing.  The  electric  circuit  is  thus  completed  between 
the  button  and  body  of  the  primer  across  the  platinum  bridge.  The 
priming  charge  of  gun  cotton  surrounds  the  bridge  inside  the  prongs 
of  the  support. 

The  frictional  element  is  operated  by  pulling  the  teeth  of  the  serrated 
cylinder  quickly  through  the  pellet  of  friction  composition  which  is 
ignited  by  frictional  heat  and  fires  the  -primer.  The  electrical  element 
is  operated  by  the  passage  of  the  electric  current  over  the  bridge, 
which  ignites  the  gun  cotton  and  in  turn  fires  the  primer. 

Percussion  Primers. — Primers  of  this  class  consist  of  those  which 
can  be  exploded  by  a  sharp  blow  or  frictional  shock.  The 'essential 
parts  of  a  simple  percussion  primer  are  the  primer  cup,  the  anvil  and 
the  percussion  composition.  With  the  exception  of  the  tin-foil  covering 
all  metal  parts  of  percussion  primers  are  made  of  brass.  Percussion 
primers  are  used  in  all  guns  provided  with  percussion-firing  mechanism, 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  287 

such  as  the  1 -pounder  pom-pom,  the  1.65  Hotchkiss,  the  6-pounder 
rapid-fire  gun,  the  4.7  and  the  6-inch  Armstrong  gun,  and  the  3-inch 
15-pounder  r.  f.  gun.  The  ingredients  of  the  friction  composition  con- 
sist of  the  following  mixture :  Chlorate  of  potash,  sulphide  of  antimony, 
glass  and  sulphur.  Formerly  the  composition  of  all  service  primers 
contained  a  large  percentage  of  fulminate  of  mercury,  but  on  account 
of  the  danger  involved  in  handling  these  primers  in  shipment,  its 
use  has  been  discontinued. 

To  insure  the  ignition  of  smokeless  powder  charges  in  cartridge 
cases  it  is  necessary  that  primers  either  contain  in  themselves,  in  addition 
to  the  percussion  composition,  an  auxiliary  charge  of  black  powder, 
or  that  an  auxiliary  charge  of  loose  black  powrder  be  placed  at  the 
rear  of  the  cartridge  case  to  communicate  the  flame  from  the  percussion 
primer  and  thoroughly  ignite  the  smokeless  powder. 

All  percussion  primers  now  used  in  the  service,  except  the  primer 
known  as  battery  cup,  shown  in  Fig.  30,  contains  an  igniting  charge 
of  black  powder  in  addition  to  the  essential  elements  named  above. 

PERCUSSION-PRIMER  CUP 
BODY (BRASS) 

PERCUSSION  COMPOSITION 
TIN  FOIL 

FIG.  30. 

The  amount  of  loose  black  powder  required  as  an  igniting  charge 
for  smokeless  powder  to  give  anywhere  like  uniform  ignition  is  relatively 
large,  with  the  result  that  considerable  fouling  of  the  gun  occurs  when 
the  igniting  charge  is  used.  This  is  at  all  times  objectionable,  but  is 
especially  so  with  machine  guns.  This  objection  has  resulted  in  the 
development  of  two  sizes  of  percussion  primers,  one  known  as  the 
110-grain  percussion  primer,  for  use  in  all  cartridge  cases  from  the 
1 -pounder  to  the  6-inch  Armstrong,  and  the  other  known  as  the  20-grain 
percussion  primer,  which  is  used  in  the  smaller  calibers  of  guns. 

The  110-grain  percussion  primer,  shown  in  Fig.  31,  consists  of  the 
parts  indicated  in  the  cut.  The  body  is  3J  inches  long,  and  is  drawn 
from  a  disk  of  cartridge  metal.  In  the  rear  of  the  body  a  recess  or 
pocket  for  the  percussion  primer  is  formed.  The  percussion  primer 
consists  of  a  cup,  a  percussion  composition  and  the  anvil,  is  assembled 
and  inserted  as  a  unit  into  the  pocket.  A  hole  is  drilled  through 
the  diaphragm  separating  the  pocket  from  the  cavity  containing  the 
compressed  charge  to  allow  passage  of  the  flame  from  the  percussion 
primer. 


288 


THE  SERVICE  OF  COAST  ARTILLERY 


The,  primer  charge  consists  of  110  grains  of  black  powder  inserted 
under  a  pressure  of  36,000  Ibs.  per  square  inch.  Eight  radial  holes  are 
drilled  through  the  primer  and  compressed  powder.  The  powder  is 
pressed  into  the  primer  body  around  a  central  wire,  which  is  then 
withdrawn,  leaving  a  longitudinal  hole  the  full  length  of  the  primer. 


BODY  (BRASS) 
PERCUSSION-PRIMER 
CUP  AND  COMPOSITION 

ANVIL 

COMPRESSED  POWDER 

(110  GR.) 
TIN  FOIL 


END  CLOSING  WAD 
(PAPER) 

FIG.  31. 


This  compression  of  the  powder  with  the  longitudinal  hole  increases 
the  time  of  burning  of  the  powder  charge,  and  causes  the  primer  to  burn 
with  a  torchlike  rather  than  an  explosive  effect,  making  the  ignition 
of  the  smokeless  powder  charge  more  complete.  This  primer  has  been 

PERCUSSION-PRIMER  CUP 
PERCUSSION  COMPOSITION 
COMPRESSED  POWDER 
TIN-FOIL  COVERING 

END  CLOSING  WAD (PAPER) 

FIG.  32. 

adopted  for  use  in  all  cartridge  cases  from  the  6-pounder  to  the  6-inch 
Armstrong  inclusive,  and  requires  no  rear  igniting  charge. 

The  primer  is  a  drive  fit  in  its  seat  in  all  cartridge  cases  in  which 
it  is  used,  and  for  this  reason  a  special  press  for  the  insertion  of  the 
primer  is  provided. 

The  20-grain  percussion  primer  shown  in  Fig.  32  has  been  adopted 


PLATE   XX 


1.  Point  Fuse,  Minor  Caliber. 

2.  Base  Fuse,  Minor  Caliber. 

3.  Base  Fuse,  C  High. 

4.  Centrifugal  F  Fuse  Altered  C. 

5.  Centrifugal  F  Fuse. 

6.  Centrifugal  S  Fuse  Altered  A. 

7.  Centrifugal  S  Fuse. 


Types  of  Fuses. 

8.  Centrifugal  12  M  Fuse. 

9.  15-second  F.A.  Combination  Fuse 

10.  Combination  Fuse  28-second  High. 

11.  Combination  Fuse  28-second  Low. 

12.  Erhardt  Combination  Fuse. 

13.  Krupp  Combination  Fuse. 

14.  Combination  Fuse,  F.A.  21-second. 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES 


289 


for  use  in  cartridge  cases  for  1-pounder  subcaliber  tubes,  percussion 
firing,  1-pounder  machine  guns,  and  the  1.65  Hotchkiss.  Its  con- 
struction is  practically  the  same  as  that  of  the  1  ID-grain  percussion 
primer,  the  main  difference  being  that  the  primer  charge  consists  of 


PERCUSSION-PRIMER  CUP 
PERCUSSION  COMPOSITION 
ANVIL 

LOOSE  POWDER(20  (JR.) 

END  CLOSING  WAD (PAPER) 
FIG.  33. 


only  20  grains  of  compressed  powder  inserted  under  the  same  pressure 
as  the  larger  primer. 

For  saluting  purposes  the  percussion  saluting  primer,  shown  in 
Fig.  33,  has  been  adopted.  It  is  used  in  all  saluting  cases  for  guns 
designated  as  using  110-grain  percussion  primers. 


VENT  CLOSING  DISK (PAPER) 
BODY  (BRASS) 
OBTURATING  CUP (BRASS) 
OBTURATING  VALVE (BRASS) 

PRIMER  CHARGE 

END  CLOSING  WAD 
(PAPER) 

FIG.  35. 


FIG.  34. 


FIG.  36. 


For  use  in  the  smaller  guns  the  percussion  primer  battery  cup, 
shown  in  Fig.  30,  is  used  in  all  fixed  ammunition. 

Igniting  Primers. — Primers  of  this  class  consist  of  those  which  con- 
tain no  means  of  ignition  within  themselves,  but  require  for  their 
ignition  an  auxiliary  friction  or  electric  primer  which  is  inserted  in 


290  THE  SERVICE  OF  COAST  ARTILLERY 

the  vent  of  the  piece  in  the  same  manner  as  for  service  firing.  Igniting 
primers  consist  essentially  of  a  brass  body,  an  obturating  cup,  an 
obturating  valve,  a  vent-closing  disk,  an  end-closing  wad,  and  a  20-grain 
primer  charge.  They  are  assembled  as  shown  in  Figs.  34,  35,  and  36. 
The  saluting  igniting  primer,  shown  in  Fig.  35,  is  designed  for  use  in 
cartridge  cases  for  18-pounder  subcaliber  guns  in  firing  blank  charges 
of  black  powder. 

The  action  of  the  primer  is  as  follows :  The  flames  and  gases  from  the 
auxiliary  primer  cut  through  the  vent  in  the  cap  and  drive  the  obturating 
valve,  which  is  normally  in  the  rear  of  the  cup,  closing  the  vent  forward, 
allowing  the  flames  to  pass  around  and  enter  the  primer  cavity  through 
the  vent  in  the  diaphragm,  and  thus  igniting  the  primer  charge.  The 
pressure  of  the  gases  at  once  react  on  the  obturating  valve  and  drive 
it  to  the  rear,  closing  the  vent  in  the  obturating  cup,  at  the  same  time 
expanding  the  walls  of  the  cup  in  the  recess,  making  a  gas  check  at 
both  these  points. 

The  powder  charge  of  this  primer  consists  of  20  grains  of  loose 
rifle  powder. 

The  flame  from  the  service  primer  alone  would  not  be  sufficient  to 
ignite  properly  the  smokeless  powder  charge  in  the  cartridge  case,  and 
therefore  the  igniting  primer  is  used. 

The  110-grain  igniting  primer  is  identical  in  form  and  dimensions 
with  the  110-grain  percussion  primer,  and  is  designed  for  use  in  cart- 
ridge cases  for  subcaliber  practice  with  the  18-pounder  subcaliber  guns 
only.  Its  action  is  the  same  as  that  described  for  the  saluting  igniting 
primer.  Its  primer  charge  consists  of  110  grains  of  rifle  powder. 

The  20-grain  igniting  primer,  shown  in  Fig.  36,  bears  the  same 
relation  to  the  20-grain  percussion  primer  as  the  110-grain  igniting 
primer  does  to  the  110-grain  percussion  primer.  It  is  designed  for  use 
in  cartridge  cases  for  the  1 -pounder  subcaliber  guns  in  subcaliber 
practice,  and  requires  no  igniting  charge  of  black  powder. 

FUSES 

(See  Plate  XX) 

Fuses  are  devices  used  to  ignite  or  detonate  bursting  charges  con- 
tained in  projectiles.  They  are  classified:  (1)  According  to  their 
construction,  as  Ring-Resistance;  Centrifugal;  Combination;  Detonat- 
ing. (2)  According  to  their  use,  as  Time,  Percussion,  Combination 
Time  and  Percussion.  (3)  According  to  their  location  in  the  projectile, 
as  Point  or  Base. 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  291 

The  essential  elements  common  to  all  fuses  of  whatever  class  are 
safety  in  handling  and  transportation;  certainty  in  action  when  fired; 
suitability  for  use  in  projectiles  of  different  calibers;  simplicity  in 
construction  ;  cheapness  of  manufacture  ;  stability  in  storage  and 
method  of  assembly. 

Ring-Resistance  Fuses  are  made  both  for  base  and  point  insertion, 
and  consist  essentially  of  a  fuse  stock  or  body,  firing-pin  sleeve,  split- 
ring  spring,  firing  pin,  percussion  primer  and  fuse  cap. 

There  are  two  classes  of  resistance  fuses  manufactured,  the  "  high 
resistance"  and  the  "low  resistance/'  so  called  because  the  arming 
resistance  of  the  ring  is  relatively  high  or  low,  that  is,  the  resistance 
of  the  spring  requires  a  greater  or  less  shock  to  arm  them.  High- 
resistance  fuses  are  safe  under  all  ordinary  conditions  of  handling  and 
transportation,  and  may  be  transported  fixed  in  the  projectiles  in  which 
it  is  intended  to  use  them.  Low-resistance  fuses  cannot,  on  account 
of  the  danger  of  premature  arming,  be  transported  inserted  in  projectiles. 
They  are  shipped  in  hermetically  sealed  boxes,  and,  to  prevent  prema- 
ture arming  of  the  plunger  in  handling,  the  firing-pin  sleeve  and  firing 
pin  are  locked  together  by  means  of  a  safety  wire  passing  through  them 
and  the  body  of  the  fuse.  Just  before  using,  this  wire  must  be  pulled 
out,  after  which  the  fuse  may  be  screwed  into  the  projectile. 

All  the  fuses  of  this  class  issued  to  the  service  at  present  belong  to 
the  high-resistance  class,  the  only  low-resistance  fuses  at  present  issued 
to  the  service  being  the  22-secorid  combination  fuse,  low  resistance, 
for  use  in  a  7-inch  mortar  shot.  All  service  fuses  are  stamped  to  show 
the  distinguishing  letter  of  designation  and  place  of  manufacture.  The 
point  fuses  have  a  right-hand  thread,  which,  in  connection  with  the 
right-hand  twist  of  rifling,  has  a  tendency  to  tighten  in  its  seat  on 
discharge.  For  the  same  reason  all  base  fuses  have  a  left-hand  thread. 

The  arming  resistance  of  ring-resistance  fuses  is  tested  in  the  course 
of  manufacture  with  a  static  machine,  which  gives  the  weight  necessary 
to  force  the  sleeve  over  the  firing  pin  against  the  resistance  of  the  split- 
ring  spring.  They  are  also  tested  by  assembling  them  in  shell  and 
dropping  the  shell  upon  a  steel  plate. 

Ring-resistance  fuses  are  also  percussion  in  their  character,  that  is, 
the  shock  of  discharge  prepares  the  fuse  for  action  and  the  shock  of 
impact  causes  the  fuse  to  act.  A  type  of  ring-resistance  point-percussion 
fuse  for  minor  caliber  guns  is  shown  in  Fig.  37  (before  arming  and 
after  arming).  The  same  type  of  fuse  for  base  percussion  is  shown 
in  Fig.  38. 

The  fuse  itself  is  a  small  affair  relatively,  but  its  importance  cannot 


292 


THE  SERVICE  OF  COAST  ARTILLERY 


be  overrated.  All  percussion  fuses  carry  an  interior  mass  called  the 
plunger,  whose  forward  movement,  when  the  shell  is  retarded,  causes 
the  firing  pin  to  strike  a  percussion  primer  and  explode  it.  Before 
firing  the  fuse  must  be  in  a  "  safe  "  or  "  unarmed  "  condition,  in  which 


BEFORE  ARMING 


AFTER  ARMING 

85- 


TIN-FOIL  DISC 

PRIMER  CHARGE 

(BLACK  POWDER) 

PRIMER  SHIELD 

(BRASS) 


BODY  (BRASS) 
PERCUSION- 
PRIMER  CUP 
PERCUSSION- 
PRIMER  SCREW 
PERCUSSION 

COMPOSITION 
FIRING  PIN 

IRING  PIN 

SLEEVE 
SPLIT-RING 
LOCKING  GROOVE 
CLOSING  SCREW 


FIG.  37. — Ring  Resistance  Point  Percussion  Fuse.     For  minor  cailbers. 

the  pin  cannot  reach  the  primer,  and  during  the  flight  of  the  projectile 
it  must  be  in  the  "ready"  or  "armed  "  position.  Either  or  both  of  the 
forces  exerted  on  the  plunger  to  give  it  the  longitudinal  and  angular 
accelerations  communicated  to  the  projectile  may  be  utilized  to  trans- 


BEFORE  ARMING 


PRIMER 
CHARGE 
PRIMER 
SHIELD 
Q3RASS) 

LOCKING 
GROOVE 


CAP (BRASS) 
CLOSING- 
DISC  (BRASS) 
PRIMER- 
SCREAK  BRASS) 
PERCUSSION- 
COMPOSITION 
FIRING  PIN- 

SPLIT-RING 

SPRING (BRASS) 

BODY( BRASS) 


FIG.  38. — Ring  Resistance  Base  Percussion  Fuse.     For  minor  calibers. 

form  the  plunger  from  the  "safe"  to  the  "ready"  position.  The 
fuse  is  made  principally  of  hard  rolled  brass.  The  body  which  forms 
a  housing  for  the  parts  of  the  fuse  is  struck  at  the  head  with  a  radius 
corresponding  to  that  of  the  shell  in  which  used.  Two  slots  are  formed 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  293 

in  the  head  for  a  spanner  wrench  for  insertion  and  removal  of  the  fuses 
from  the  projectiles.  The  outside  of  the  body  is  turned  and  threaded, 
and  the  interior,  after  being  bored  out  for  the  plunger  and  primer  parts, 
is  threaded  for  the  closing  screw.  The  front  end  of  the  plunger  cavity 
is  bored  out  to  form  a  recess  for  the  primer,  and  is  threaded  with  a 
left-hand  thread  in  the  interior  for  the  primer  screw.  A  hole  in  the 
top  of  the  primer  screw  permits  the  firing  pin  to  strike  the  primer  on 
impact,  and  allows  the  flame  to  come  from  the  primer  in  the  rear  and 
ignite  the  shell  charge.  The  primer  screw  holds  the  primer  cup  in 
place,  which  is  longer  than  the  recess  in  the  primer  screw,  so  that  when 
the  latter  is  screwed  down  hard  it  bears  upon  the  bottom  of  the  primer 
recess. 

The  primer  cup  has  two  chambers  separated  by  a  solid  vented  par- 
tition; the  lower  chamber  holds  the  percussion  composition,  which  is 
held  in  place  by  the  primer  shield,  which  also  restrains  the  firing  pin 
during  the  flight  of  the  projectile. 

In  unarmed  or  safe  condition  of  the  fuse,  the  split  ring  rests  on  a 
conical  slope  on  the  firing  pin  and  sustains  the  firing  pin  on  the  sleeve. 
The  resistance  of  this  ring  to  the  expansion  necessary  to  force  it  ov.er 
the  slope  is  less  than  the  force  required  to  transmit  the  maximum  ac- 
celeration of  the  projectile  to  the  sleeve,  thus  insuring  the  arming  of 
the  fuse  in  the  bore  of  the  gun  on  discharge.  The  percussion  com- 
position of  all  service  fuses  consists  usually  of  the  following  ingredients : 
Chlorate  of  potash,  sulphide  of  antimony,  sulphur,  ground  glass  and 
shellac.  The  ingredients  are  mixed  dry,  alcohol  being  added  to  absorb 
the  shellac. 

The  action  of  the  fuse  is  as  follows.  When  the  piece  is  fired  the 
sleeve  moves  to  the  rear,  and  is  locked  to  the  firing  pin,  the  point  of 
the  firing  pin  projecting  beyond  the  sleeve  and  thus  arming  the  fuse. 
As  the  projectile  meets  the  atmospheric  retardation  the  plunger  grad- 
ually creeps  forward  until  stopped  by  the  primer  shield.  When  the 
projectile  strikes,  the  firing  pin  pierces  the  shield  and  the  thin  layer 
of  percussion  composition,  and  ignites  the  primer  charge.  This  is 
done  by  a  small  portion  of  the  composition  being  caught  between  the 
point  of  the  firing  pin  and  the  anvil. 

The  action  of  the  base  percussion  fuse  and  the  function  of  its  parts 
are  the  same  as  those  for  the  point  percussion,  the  only  essential  differ- 
ence being  the  position  of  the  primer  with  reference  to  the  shell  charge. 
In  the  case  of  the  point  fuse  the  flame  from  the  primer  has  to  pass 
either  through  or  around  the  plunger  from  front  to  rear,  but  in  the  case 
of  the  base  fuse  the  flame  does  not  have  to  cross  any  intervening  space. 


294 


THE  SERVICE  OF  COAST  ARTILLERY 


BEFORE  ARMING 


PRIMER  DISC 
(TIN  FOIL) 
TIRING  PIN  „ 
LINK  (BRASS) 
PERCUSSION 
PLUNGER 

ARMING  RE- 
SISTANCE 
BOLT  &  NUT 
PERCUSSION- 
PLUNGER  BUSH- 


PRIMER  CLOSING 
*  SCREW 

CLOSING  CAP  SCREW 
PRIMER  CUP 
RESTRAINING  DISC 
__._  PIN (BRASS) 
PERCUSSION  PLUNGER 


AFTER  ARMING 
9 


ROTATING  FIN(BRASS) 
30DY   (BRASS) 


FIG.  39.— Centrifugal  Base  Fuse  F. 


PRIMER  DISK   BEFORE  ARMING 
(TIN  FOIL) 

PRIMER  DISK 
(TIN  FOIL) 

FIRING  PIN 

LINK(BRASS) 

PERSUSSION 

PLUNGER 

PERCUSSION 
PLUNGER  BUSHING 


AFTER  ARMING 


PRIMER  CLOSING  SCREW 
CLOSING  CUP  SCREW 

PRIMER  CUP  (BRASS) 
RESTRAINING  DISK 
FIRING  PIN  (BRASS) 
PERCUSSION  PLUNGER 
ARISING  RESISTANCE 
BOLT  AND  NUT 
ARMING  RESISTANCE 
SPRING 
ROTATING  FIN 

BODY  (BRASS) 


FIG.  40. — Centrifugal  Base  Percussion  Fuse.     Medium  and  major  caliber. 
BEFORE  ARMING 


PRIMER  DISK: 

(TIN  FOIL) 

PRIMER  DISC 
(TIN  FOIL) 


FIRING  PIN 
LINK 

PERCUSSION 
PLUNGER 
BUSHING 


PRIMER  CLOSING  SCREW 
CLOSING  CAP  SCREW 
PRIMER  CUP 
RESTRAINING  DISK 
FIRING  PIN 

PERCUSSION  PLUNGER 
ARMING  RESISTANCE 
BOLT  AND  NUT 

ARMING  RESISTANCE 

SPRING 
.ROTATING  FIN 


BODY  (BRASS) 


FIG.  41.— Centrifugal  Base  Fuse,  12M. 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  295 

Centrifugal  Fuses  depend  for  their  action  on  the  centrifugal  force 
developed  by  the  rotation  of  the  projectile.  The  increased  rapidity 
of  fire  renders  it  necessary  for  all  fuses  to  be  transported  fixed  in  pro- 
jectiles, as  too  much  time  would  be  lost  under  war  conditions  if  fuses 
had  to  be  unpacked  and  inserted  during  an  engagement.  The  require- 
ment also  that  the  projectiles  fused  shall  be  handled  and  transported 
with  absolute  safety  is  a  reason  which  led  to  the  development  of  the 
centrifugal  fuse. 

As  has  been  stated  in  the  case  of  ring  resistance  fuses,  or  any  fuse 
the  action  of  which  depends  upon  the  longitudinal  stresses  developed 
by  the  pressure  of  the  powder  gases  of  the  gun  on  discharge,  the  con- 
ditions of  safety  of  handling  and  certainty  of  action  were  imposing 
ones. 

A  centrifugal  fuse  is  armed  by  the  centrifugal  force  developed  by  the 
rotation  of  the  projectile,  and  is  safe  until  the  maximum  velocity  of 
rotation  is  nearly  attained.  The  three  principal  types  of  centrifugal 
fuses  are  shown  in  Figs.  39,  40  and  41.  The  fuse  body  or  stock  and 
the  primer  parts  of  the  centrifugal  fuse  do  not  differ  materially  from  the 
corresponding  parts  of  ring-resistance  fuses.  The  body  of  the  centrif- 
ugal plunger  is  in  three  parts,  nearly  semi-cylindrical  in  shape,  which 
when  the  fuse  is  at  rest,  are  held  together  by  the  pressure  of  a  spiral 
spring  contained  in  the  cylindrical  bushing  which  is  secured  to  one  of 
the  plunger  halves.  The  spring  exerts  its  pressure  on  the  other  half 
cf  the  plunger  through  a  bolt.  Pivoted  in  a  recess  in  one-half  of  the 
[-lunger  is  the  firing  pin,  which,  when  the  fuse  is  at  rest,  is  held  with  its 
point  below  the  front  surface  of  the  plunger  by  the  lever  action  of  the 
link  which  is  pivoted  in  the  other  half.  Under  the  action  of  centrif- 
ugal force  developed  by  the  rapid  rotation  of  the  projectile  the  two 
halves  of  the  plunger  separate.  This  separation  causes  the  rotation  of 
the  firing  pin,  the  point  of  which  is  then  held  in  advance  of  the  front 
surface  of  the  plunger,  ready,  on  impact  of  the  projectile,  to  pierce  the 
brass  primer  shield  and  ignite  the  percussion  composition.  When  the 
fuse  is  armed  the  end  of  the  link  rests  on  the  axis  of  the  firing  pin,  thus 
affording  support  to  the  firing  pin  when  it  strikes  the  percussion  primer. 
The  separation  of  the  plunger  parts  is  limited  by  a  nut  coming  to  a 
bearing  on  a  shoulder  on  the  bushing,  so  as  not  to  permit  the  diameter 
of  the  expanded  plunger  to  equal  the  interior  diameter  of  the  fuse 
stock. 

A  rotation  piece  is  screwed  into  the  head  of  the  fuse  stock,  and 
engages  in  a  corresponding  slot  cut  through  the  bottom  of  both  plunger 
halves  and  insures  the  rotation  of  the  plunger  with  the  shell.  The 


296 


THE  SERVICE  OF  COAST  ARTILLERY 


BEFORE  ARMING 


CONCUSSION  OR 

TIME  PLUNGER 


POWDER  RING 


RETAINING  RING 
BRASS  WASHER 


GAS  CHECK  CUP 
PELT  GAS  CHECK 


BASE  COVER 


CAP  (BRASS) 
SAFETY  PIN 
SPLIT-RING  SPRING 
CLAMPING  RING 

PERCUSSION 
COMPOSITION 
TIMS  TRAIN 
CQITE(LEAD) 
CONE  COVER 
TIME  TRAIN 


BODY (BRONZE) 

PERCUSSION 

PRIMER 
PERCUSSION 
FIRING  PIN 


SLEEVE 


PAPER  DISC 


\.       X'  JUJ.l«kAJV4    J-  JL, 

0\PERCUSSION 
\  FIRING  PIN 

^SPLIT  RING  PER- 
CUSSION PLUNGER 

'CLOSING  SCREW 


FIG.  42. — Combination  Fuse,  15-second  (Frankford  Arsenal). 


AFTER  ARMING 


CONCUSSION  FIRING- 


PIN    (STEEL) 
VENTS . 


CONNECTING  TUB: 
CLOSING  SCREW 


CONE  DOWEL  PINS 

(BRASS) 
WRENCH  HOLE 
COVER  DOWEL  PINS 


FIG.  43. — Combination  Fuse,  15-second  (Frankford  Arsenal) 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  297 

strength  of  the  spring  is  so  adjusted  that  the  fuse  will  not  arm  until 
its  rapidity  of  revolution  is  a  certain  percentage  of  that  in  the  shell 
in  which  it  is  used,  and  that  it  will  certainly  arm  when  the  rapidity  of 
revolution  approximates  that  expected  in  the  shell.  Should  the  parts 
of  the  plunger  be  accidentally  separated  and  the  fuse  armed  by  a 
sudden  jolt  or  jar  in  transportation  or  handling,  the  reaction  of  the 
spring  will  immediately  bring  the  plunger  to  the  unarmed  position. 

Centrifugal  plungers  are  used  as  base  percussion  fuses  in  the  small, 
medium,  and  large-caliber  guns,  howitzers  and  mortars,  also  as  base- 
detonating  fuses  in  the  medium  and  large  caliber  as  well  as  the  per- 
cussion plunger  in  combination  fuses. 

The  greater  simplicity  and  cheapness  of  the  ring-resistance  fuse  and 
its  greater  certainty  of  action  make  it  more  suitable  for  use  whenever 
practicable. 

Combination  Fuses  used  in  the  service  are  point  insertion  and 
combine  the  elements  of  time  and  percussion  arranged  to  act  indepen- 
dently in  one  fuse  body.  Combination  fuses  contain  two  plungers  and 
two  primers,  arming  and  firing  by  concussion  and  percussion,  respec- 
tively. The  concussion  plunger  arms  and  fires  the  percussion  primer 
by  shock  of  discharge  in  the  bore  of  the  gun  and  ignites  the  time  ele- 
ment. The  percussion  plunger  is  armed  by  the  shock  of  discharge  and 
fires  its  primer  on  impact. 

There  are  at  present  two  general  classes  of  combination  fuses  in 
the  service,  differing  principally  in  the  details  of  the  time-train  elements. 
In  the  first  class  this  element  consists  of  a  wire-drawn  lead  tube  filled 
with  meal  powder  wound  in  a  spiral  groove  around  the  lead  core.  In 
the  second  class  this  element  consists  of  two  superposed  trains  of  meal 
powder  compressed  with  heayy  pressure  in  annular  grooves  in  disks 
of  brass. 

The  first  class  is  shown  in  Figs.  42  and  43,  the  second  class  is  repre- 
sented in  Figs.  44,  45  and  46.  JiTo  more  fuses  of  the  first  class  are  to 
be  manufactured,  those  of  the  second  class  having  been  found  far 
superior  in  many  respects.  The  combination  fuse  of  the  first  class 
cannot  be  reset,  while  those  of  the  second  class  can  be  reset  many  times 
if  desired.  This  fuse  is  also  superior  in  that  it  has  greater  uniformity 
of  action  clue  to  the  improvement  in  the  time-train  feature.  The 
fuses  of  class  one  have  the  time-train  element  composed  of  the  concus- 
sion or  time  plunger,  the  firing  pin,  the  cone,  the  time  train,  the  cone 
cover,  the  cap  and  the  clamping  nut.  The  plunger  is  cylindrical  in 
shape  and  contains  the  fulminate  primer  in  a  recess  in  its  base.  Its 
upper  extremity  is  pierced  to  receive  a  safety  pin  which  retains  the 


298  THE  SERVICE  OF  COAST  ARTILLERY 

plunger  in  its  safe  or  unarmed  position  in  handling  and  transportation. 
When  the  safety  pin  is  removed,  which  is  done  just  before  firing,  the 
weight  of  the  plunger  rests  on  the  split-ring  spring.  The  action  of  the 
latter  on  discharge  is  similar  to  that  of  the  split-ring  spring  of  other 
ring-resistance  fuses  already  described. 

The  cone  is  an  alloy  of  soft  metal  held  in  place  on  the  fuse  body 
by  a  clamping  nut  and  a  groove  at  the  bottom,  and  is  prevented  from 
turning  by  four  steel  dowel  pins.  The  lip  on  the  bottom  of  the  cone, 
entering  the  groove  in  the  body,  acts  as  a  gas  check  to  prevent  the 
ignition  of  the  powder  in  the  connecting  tube.  On  the  exterior  of 
the  cone  is  a  left-handed  groove  which  carries  the  time  train,  and  this 
time  train  communicates  at  its  lower  end  with  the  priming  charge 
in  the  tube  and  thence  with  the  magazine.  The  time  train  is  formed 
of  a  lead  tube  filled  with  meal  powder  and  is  wire  drawn. 

The  cone  cover  is  of  brass,  and  is  held  in  place  by  a  cap  and  pre- 
vented from  turning  by  a  small  pin  projecting  from  the  body  and  fitting 
in  a  slot  on  its  lower  edge.  On  the  exterior  of  the  cone  is  a  left-handed 
groove  corresponding  to  that  on  the  time  train,  and  this  groove  is 
pierced  with  holes  numbered  from  1  to  15  or  1  to  21  or  1  to  28  as  the 
case  may  be,  these  numbers  corresponding  to  the  number  of  seconds, 
the  spaces  between  the  holes  being  divided  into  5  equal  parts,  or  fifths 
of  seconds.  The  percussion  element  may  consist  of  either  the  ring- 
resistance  plunger  or  the  centrifugal  plunger,  depending  upon  the  type 
of  fuse  considered. 

The  action  of  the  fuse  is  as  follows:  As  a  time  fuse:  A  hole  is 
punched  through  the  cover,  time  train  and  lead  cone,  at  the  point  in 
the  cover  corresponding  to  the  number  of  seconds  desired.  Before 
loading  the  safety  pin  is  removed,  and  this  allows  the  time  plunger  to 
rest  on  the  fuse  body,  where  it  is  held  by  the  split-ring  spring.  The 
projectile  is  then  inserted  in  the  gun.  By  the  shock  of  discharge  the 
split-ring  spring  is  expanded  and  the  plunger  forced  to  the  rear,  the 
primer  striking  the  firing  pin  and  exploding.  The  flame  from  the 
primer  passes  through  the  four  radial  holes  and  ignites  the  ring  of 
compressed  powder.  The  only  vent  for  these  gases  is  a  punched  hole, 
and  they  ignite  the  time  train  at  that  point.  The  train  burns  and 
ignites  the  powder  in  the  tube  and  the  magazine.  The  flame  from 
the  magazine  passes  through  the  percussion  primer  and  percussion- 
plunger  chamber  and  ignites  the  bursting  charge  in  the  shell. 

As  a  percussion  fuse:  The  percussion  plunger  arms  by  shock  of 
discharge  and  fires  the  percussion  primej  on  impact  as  in  other  per- 
cussion fuses.  The  percussion  plunger  is  grooved  or  fluted  to  permit 


EXPLOSIVES,   PROJECTILES,   PRIMERS  AND  FUSES 


299 


ready  passage  of  the  flame  from  the  front  to  the  rear.  In  order  to  use 
this  fuse  in  base  charge  shrapnel  an  extension  piece  is  necessary,  and 
is  screwed  in  the  base  of  the  fuse  in  place  of  the  bottom-closing  screw. 
The  ignition  of  the  pellet  of  compressed  powder  in  the  extension  piece 
transmits  the  flame  through  the  central  tube  to  the  base  charge. 


BEFORE  ARMING 


TIME  OR  CONCUSSION  PLUNG 
SPLIT  RING  SPRING  (BRASS) 
FRONT  CLOSING  CAP  (BRONZE 
FIRING  PIN  (BRASS) 
UPPER  TIME  TRAIN  RING 

(BRONZE) 
CLOTH  WASHER 


LOWER  TIME  TRAIN  RING 
CLOTH  WASHER 


PERCUSSION  PRIMER 
POWDER  MAGAZINE 


LINEN  GAUZE 


BODY  (BRONZE) 
FRONT  CLOSING  CAP 
VENT  TO  UPPER  TRAIN 
.COMPRESSED  POWDER  PELLET 
.UPPER  TIME  TRAIN ( COM. POW.) 

OMPRESSED  POWDER  PELLET 
IN  VENT  TO  LOWER  TRAIN 

OWER  TIME  TRAIN 

(COMPRESSED  POWDER) 


COMPRESSED  POWDER  PELLET 
IN  VENT  TO  LOWER  TRAIN 

ENT  LEADING  TO  MAGAZINE 
PERCUSSION  PLUNGER 
BOTTOM  CLOSING  SCREW 


FIG.  44. — Combination  Fuse,  21-second,  Model  of  1907. 


BEFORE  ARMING 


?IMB  OR  CONCUSSION  PLUNGER 
5)  - 


UPPER  TIME  TRAIN  (COMPRESSED  POWD! 
COMPRESSED  POWDER  PELLET  IN 
LEADING  TO  LOWER  TIME  TRAIN 


COMPRESSED  POWDER  PELLET. IN  VENT 
LEADING  TO  MAG1ZINE 
VENT  LEADING  TO  MAGAZINE 

POWDER  MAGAZINE 

ROTATING  DEVICE  (BRASS) 
LINEN  GAUZE 


BODY    (BRONZE) 

FRONT  CLOSING 
CAP    (BRONZE) 


_._.  TIME  TRAIN 
RING    (BRONZE) 
CLOTH  WASHER 
LOWER   TIME  TRAIN 
^IWG    (BRONZE 
LOTH  WASHER 


ERCUSSION  PRIMER 
•CENTRIFUGAL 
•PERCUSSION  PLUNGER 
CLOSING   CUP (BRASS) 
CLOSING  SCREW(BRASS) 
•WASHER  (BRASS) 


FIG.  45. — Combination  Fuse  (Centrifugal)  21-second  (Frankford  Arsenal). 

The  latest  types  of  combination  fuses  are  those  shown  in  Figs. 
44,  45  and  46,  and  belong  to  class  two.  The  body  of  the  fuse  and  the 
front  closing  cap  are  machined  from  bronze  castings.  The  upper  and 
lower  time-train  rings  are  turned  from  hard  rolled  rods  of  Tobin  bronze. 
An  annular  groove  in  the  shape  of  a  horseshoe  is  milled  in  the  lower 
face  of  each  of  the  time-train  rings.  Meal  powder  is  compressed  in 
these  grooves  under  a  pressure  of  70,000  pounds  per  square  inch, 
forming  a  time  train  of  necessary  length. 

The  time  element  of  this  fuse  consists  of  the  following  parts:     The 


300 


THE  SERVICE  OF  COAST  ARTILLERY 


time  or  concussion  plunger,  the  split-ring  spring,  the  firing  pin,  the  vent 
leading  to  the  upper  time  train,  the  compressed  powder  pellet,  lower 
time  train,  the  compressed  powder  pellet  in  the  vent  leading  to  the 
powder  magazine. 

The  upper  ring  is  prevented  from  rotating  by  pins  which  are  halved 
into  the  fuse  body  and  the  inner  circumference  of  the  ring.  A  vent  is 
drilled  through  the  walls  of  the  percussion  chamber  and  is  exactly 
opposite  a  hole  in  the  inner  surface  of  the  upper  time  train  leading  to 
the  end  of  the  train  from  which  the  direction  of  burning  is  anti-clock- 
wise. Another  hole  is  drilled  through  the  upper  face  of  the  lower 


EXTERIOR 


RETAINING  WIRE 


COMPRESSED  POWDER  PELLET 
IN  UPPER  TIME- TRAIN  VENT 
COMPRESSED  POWDER  PELLET 
IN  LOWER  TIME- TRAIN  VENT 
FUZE  SETTER  STUD(BRASS) 


FIG.  46.— Combination  Fuse,  21-second,  Model  of  1907. 

time-train  ring,  to  the  end  of  the  lower  time-train  groove  from  which 
the  direction  of  burning  is  clockwise.  The  lower  time-train  ring  is 
immovable  and  is  graduated  on  its  outer  edge  in  a  clockwise  direction 
from  0  to  21,  each  full  division  corresponding  to  one  second  of  time  of 
burning  in  flight.  These  divisions  are  subdivided  into  five  equal  parts 
corresponding  to  one-fifth  seconds.  A  fixed  pin  or  stud  is  provided  on 
the  lower  or  graduated  time-train  ring,  which  enters  a  notch  of  the 
corrector  ring  or  fuse  setter  when  set  in  a  fuse.  An  arrow  on  the 
lower  side  of  the  fuse  stock  is  the  datum  line  for  the  fuse  settings. 

A  vent  is  drilled  through  the  flange  of  the  fuse  stock  to  the  powder 
magazine,  and  leads  to  the  same  end  of  the  lower  time  train  as  the 
vent  last  described;  that  is,  the  end  which  the  direction  of  burning  is 
clockwise  when  the  fuse  is  at  its  "  O  "  setting. 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  301 

The  action  of  the  time  feature  of  the  fuse  is  as  follows:  Assume 
first  the  zero  setting  as  shown  in  Fig.  46.  The  time  plunger  arms  and 
fires  the  primer  which  it  carries  as  in  the  case  of  the  first  fuse  described. 
The  flame  from  the  primer  passes  out  through  the  vent  drilled  through 
the  walls  of  the  concussion  plunger  chamber  and  ignites  the  pellet  at 
the  end  of  the  upper  time  train  (see  Fig.  44) ,  down  through  the  vent 
through  the  upper  surface  of  the  lower  time  train,  to  the  end  of  the 
lower  time  train  and  thence  through  the  vent  to  the  magazine, 
the  flame  from  which  is  transmitted  to  the  base  charge  in  the 
shrapnel. 

It  will  be  seen  that  for  the  zero  setting  of  the  fuse  the  origin  of  both 
the  upper  and  lower  time  trains  are  in  juxtaposition.  For  any  other 
setting,  say  12  seconds:  The  vent  through  the  upper  face  of  the  lower 
time  train  changes  its  position  with  respect  to  the  vent  leading  to  the 
beginning  of  the  upper  time  train  and  the  vent  leading  to  the  powder 
magazine,  both  of  which  points  are  fixed  by  the  angle  subtended 
between  the  0-  and  the  12-second  settings.  For  this  setting  the  flame 
passes  out  through  the  vent  drilled  through  the  walls  of  the  concussion 
plunger  chamber  and  burns  on  the  upper  time  train  in  an  anti-clock- 
wise direction  until  the  vent  drilled  through  the  upper  surface  of  the 
lower  time  train  is  reached,  where  it  passes  down  to  the  beginning 
of  the  lower  time  train  and  burns  back  in  a  clockwise  direction  to  the 
position  of  the  vent  leading  to  the  powder  magazine,  whence  it  is  trans- 
mitted by  the  pellet  of  compressed  powder. 

If  the  fuse  is  set  for  21  seconds,  the  vent  through  the  upper  face  of 
the  lower  time  train  is  opposite  the  end  of  the  upper  time  train  and 
the  end  of  the  lower  time  train  is  opposite  the  vent  leading  to  the 
powder  magazine.  It  will  be  seen  that  to  reach  the  magazine  and 
burst  the  shrapnel,  the  entire  length  of  time  train  in  both  rings  must 
be  burned. 

As  the  annular  grooves  in  the  lower  face  of  each  ring  for  the  powder 
trains  do  not  form  complete  circles,  a  solid  portion  being  left  between 
the  ends  of  the  grooves,  the  fuse  can  be  set  at  the  safety  point  quoted, 
which  is  indicated  by  the  letter  S,  in  which  position  the  fuse  cannot 
be  exploded. 

The  fuse  is  provided  with  cloth  washers  glued  to  the  upper  surface 
of  the  time-train  ring  and  to  the  upper  face  of  the  flange  on  the  fuse 
stock,  the  function  of  these  washers  being  to  provide  a  gas  check  and 
prevent  a  premature  action  of  the  fuse.  The  percussion  elements  of 
the  fuse  consist  of  the  percussion  plunger  and  ordinary  percussion 
primer.  The  fuse  is  also  provided  with  a  centrifugal  percussion  plunger 


302 


THE  SERVICE  OF  COAST  ARTILLERY 


which  will  take  up  immediately  the  rotation  of  the  projectile  when  a 
rotating  device,  which  consists  of  jaws  fitted  over  the  corresponding 
flat  surfaces  on  the  plunger,  is  fastened  to  the  fuse  body. 

Detonating  Fuses  are  for  use  in  shell  containing  high  explosives. 
They  are  made  for  point  and  base  insertion,  the  former  being  used  in 
the  field  shell,  the  latter  in  siege  and  seacoast  projectiles.  The  de- 
tonating fuse  differs  from  the  simple  percussion  fuse  heretofore  de- 
scribed in  having  in  addition  to  the  percussion  elements  a  detonating 
element  or  one  which  will  produce  an  explosion  of  high  order  when 
burst  in  a  projectile  containing  a  charge  of  high  explosive. 

DETONATING   FUSES 


Official  Designation  of  Fuse. 

Weight 
of  Fuse, 
in 
Pounds. 

Projectiles  in  which  Used. 

Minor  caliber  base  detonating  

0.195 

In  6-pounder  and  2  38-inch  steel  shell 

Picric  acid  bursting  charge. 

Special  "  S  "  base  fuse,  with  100  grain 
detonator         

0  65 

In  3-inch  r.f.  gun,  steel  shell  tapped  in 
base  for  this  fuse      To  be  super- 

seded by  medium  caliber  base  deto- 
nating fuse. 

Medium  caliber  base  detonating  fuse  . 

1.5 

In  all  steel  projectiles  for  guns  from 
2.95  to  7  inches  (inclusive)  in  caliber. 

Armor-piercing  base  detonating  fuse 
(modified)                             .  . 

7  09 

In  8-  10-,  and  12-inch  rifle  A.  P.  shot 
and  shell  adapted  to  the  fuse     To 

be    superseded    by    major    caliber 
detonating  fuse. 

Major  caliber  base  detonating  fuse  .  . 

2.908 

In  8-,  10-,  and  12-inch  rifle  and  mor- 
tar steel  projectiles. 

To  have  sufficient  energy  to  completely  detonate  a  high  explosive 
bursting  charge  in  projectiles  the  detonating  fuse  must  contain  high 
explosive  within  itself.  The  service  detonating  fuse  for  seacoast  pro- 
jectiles contains  two  explosive  compounds.  The  reason  for  this  is  as 
follows:  All  detonating  fuses  contain  a  percussion  plunger  either  of 
the  ring-resistance  type  or  of  the  centrifugal  type,  depending  upon  the 
projectile  in  which  used,  and  a  percussion  primer.  This  primer  con- 
sists of  the  percussion  composition  and  an  igniting  charge  of  black 
powder.  The  explosion  of  the  primer  is  of  low  order  and  would  not  of 
itself  detonate  the  high  explosive  charge  contained  in  the  fuse.  To 


EXPLOSIVES,  PROJECTILES,  PRIMERS  AND  FUSES  303 

.accomplish  this  it  is  necessary  to  introduce  between  the  percussion 
primer  and  the  detonating  charge  an  auxiliary  high  explosive  sufficiently 
sensitive  to  be  fired  by  the  percussion  primer  and  sufficiently  powerful 
to  detonate  the  high  explosive  charge  proper  contained  in  the 
fuse. 

In  order  to  contain  these  detonating  elements  it  is  necessary  for  the 
body  of  the  fuse  to  be  increased  in  length. 

The  table  on  the  preceding  page  gives  a  list  of  the  detonating  fuses 
used  in  the  steel  projectiles  containing  a  bursting  charge  of  high 
explosives. 


CHAPTER  VII 
INSTRUMENTS,   DEVICES   AND    CHARTS 

THE  various  instruments,  devices  and  charts  described  in  this 
chapter  may  be  classified  as  follows : 

Those  used  in  the  Observing  Room  for  finding  the  position  of  targets, 
which  include  the  depression  position  finders  and  the  azimuth  instrument. 
Those  used  in  the  plotting  room  for  locating  and  correcting  the  range 
and  azimuth  of  targets,  together  with  the  necessary  signal  system  inci- 
dental thereto,  which  include  the  plotting  board,  the  range  board,  the 
deflection  board,  the  wind  component  indicator,  the  aeroscope,  the  time- 
interval  bell,  the  time-interval  clock,  the  interrupter,  the  telephone  and 
telautograph. 

Those  used  in  the  Meteorological  Station  for  furnishing  data  to  the 
plotting  rooms  in  connection  with  the  condition  of  the  atmosphere 
and  the  direction  and  velocity  of  the  wind,  which  include  the  ther- 
mometer, barometer,  anemometer  and  atmosphere  board. 

Those  used  on  guns  and  mortars  for  sighting  and  laying;  also  for 
determining  the  maximum  powder  pressure  in  the  chamber,  which 
include  the  various  sights,  the  gunner's  quadrant,  and  the  crusher 
gauge. 

The  time-range  board  is  used  at  the  emplacement  to  provide 
information  for  keeping  the  piece  laid  continuously  for  range.  The 
powder  chart  is,  for  convenience,  placed  herein. 

Height  of  tide  is  received  at  the  plotting  rooms  from  the  Tide 
Station,  where  the  data  is  procured  from  a  tide  indicator,  and  sent  out 
by  means  of  the  telephone  or  the  aeroscope. 

DEPRESSION    POSITION   FINDER 

Depression  position  finders  are  arranged  for  reading  both  vertical 
and  horizontal  angles,  and  therefore,  may  be  used  as  either  depression 
position  finders,  or  as  azimuth  instruments.  Objects,  when  viewed 
from  an  elevation,  appear  under  different  angles  of  depression,  according 
to  their  distances  from  the  point  of  observation,  and  it  is  this  fact  that 

304 


PLATE   XXI 


TIME   INTERVAL  BELL 


STRIDE 

LEVEL  NUT 


ERECTING  PRISMS 
AND  HOLDER 


EST  BAR   CAP 

LEVEL  BO 


OBJECTIVE 
END  TUBE 


MICROMETER 

SCREW 


HEIGHT  SLIDE 
KNOB 


ELL  RING  SCREWS 


ILEVATING   AND 
'Z  PRESSING 
4ANOWHEEL 

PPOSITE  SIDE) 


STANDARDS 
(PART  OF  CRADLE) 


VERTICAL  SPINDLE 
BEARING 


RANGE 
POINTER 
COVER 


AZIMUTH  PLATE 
HANDLE 


LAMP   BRACKET  AND 

OPENING  FOR  READ 

!NG  HUNDREDTHS 

OF  DEGREES 


AZIMUTH  PLATE 
BOLTS     . 


READING  OPENING 
[AZIMUTH  CIRCLE  ) 


AZiMUTH  CIRCLE 
LAMP   BRACKET 


Warner  &  Swasey  D.  P.  Finder,  Type  A-l. 


INSTRUMENTS,  DEVICES  AND  CHARTS  305 

is  taken  advantage  of  in  the  depression  position  finder  when  used  to 
measure  vertical  angles. 

In  principle,  it  is  based  upon  the  solution  by  observation  of  a  vertical 
right  angle  when  given  a  side  and  two  adjacent  angles.  The  given 
side,  called  the  base,  is  the  distance  above  mean  low  water  of  the  pivot 
about  which  the  telescope  of  the  instrument  is  elevated  and  depressed. 
The  lower  angle  is  constant,  and  is  equal  to  90  degrees.  The  upper 
angle  varies  with  the  distance  of  the  observed  object. 

The  principal  parts  of  the  instrument  are  shown  in  Plate  XXI,  and 
consist  of  the  telescope,  the  cradle,  the  height  slide,  the  range  drum 
shaft,  the  range  pointer,  the  range-pointer  bracket  and  the  attachment 
for  correction  of  the  curvature  of  the  earth  and  normal  refraction,  the 
range  drum,  the  vertical  spindle,  the  azimuth  circle,  the  azimuth  worm 
screw,  the  azimuth  drum,  the  azimuth  plate,  leveling  screws,  base, 
cables,  lamp  and  lamp  brackets. 

The  principal-  parts  of  the  telescope  are  the  tube,  trunnions,  the  cell 
ring,  the  cell,  the  objective,  the  prisms,  the  micrometer  box,  cross  wires, 
micrometer  screw,  micrometer  slide,  the  draw  tube,  the  focusing  nut 
and  ring,  the  eyepiece  adapter,  the  eyepiece,  the  right  and  left  guides, 
the  level  and  the  dew  cap.  The  telescope  objective  has  a  3-inch  clear 
aperture,  and  is  provided  with  powers  12  and  20.  The  field  of  view 
is  1.85  degrees  with  both  eyepieces.  The  range  drum  is  graduated 
every  10  yards,  from  1,500  to  12,000. 

To  Use  the  Instrument  after  it  has  been  properly  mounted,  it 
should  be  first  put  in  adjustment,  and  in  doing  this,  it  may  be  found 
convenient  to  take  up  the  different  steps  in  the  following  order:  First, 
leveling.  Second,  adjustment  of  telescope.  Third,  orientation. 

First:  To  level  the  instrument,  it  should  be  set  up  so  that  it  is 
practically  level  with  equal  lengths  of  leveling  screws  exposed.  The 
cradle  can  then  be  brought  exactly  level  by  using  the  leveling  screws. 
The  cradle  is  turned  so  that  the  telescope  lies  parallel  with,  or  directly 
across  two  opposite  leveling  screws.  This  causes  the  levels  to  be 
parallel  with  opposite  leveling  screws.  The  bubble  in  each  level  is 
then  brought  to  the  center  by  turning  both  leveling  screws  either  in 
or  out,  depending  on  the  way  the  bubble  is  to  go,  a  good  rule  being 
that  the  bubble  follows  the  direction  in  which  the  left  thumb  is  turned. 
After  centering  the  bubble  with  one  set  of  screws,  do  the  same  thing 
with  the  two  other  leveling  screws,  with  which  the  other  cross  level  is 
parallel.  The  instrument  should  then  be  revolved  180  degrees,  and  if 
the  bubbles  do  not  remain  in  the  center  of  the  levels,  they  should  be 
brought  there  in  the  manner  just  described,  except  that  half  of  the 


306 


THE  SERVICE  OF  COAST  ARTILLERY 


error  in  level  should  be  corrected 
by  the  level-adjusting  screws, 
and  the  other  half  with  the 
leveling  screws.  The  instrument 
is  again  revolved  180  degrees, 
and  the  operation  repeated  until 
the  bubbles  of  the  levels  remain 
in  the  center  of  the  levels  for  all 
positions  of  the  cradle.  If  the 
range  drum  be  rotated  until  the 
reading  is  "  telescope  level,"  the 
stride  level  on  the  telescope 
should  show  the  telescope  to  be 
horizontal.  If  such  is  not  the 
case,  the  drum  should  be  rotated 
until  this  condition  is  obtained. 
The  screws  holding  the  range 
drum  to  the  beveled  gear 
loosened,  the  handle  being  firmly 
held,  the  drum  should  be  rotated 
until  the  line  corresponds  with 
that  on  the  pointer,  then  the 
screws  should  be  set  up  again. 
The  bubble  of  the  level  on  the 
telescope  should  then  remain 
stationary,  while  the  height  slide 
is  moved  to  any  position. 

Second:  Adjustment  of  the 
telescope.  The  telescope  is  a 
delicate  piece  of  apparatus,  and 
requires  careful  use  and  adjust- 
ment. Its  interior  mechanism 
is  shown  in  Fig.  47.  To  obtain 
satisfactory  results,  the  telescope 
should  have  absolute  clearness 
of  vision,  which  requires  that 
the  lenses  be  kept  free  from 
moisture,  the  erecting  prisms 
should  never  be  removed,  nor 
the  objective  lens  removed  from 
the  objective  cell  or  ring.  The 


INSTRUMENTS,  DEVICES  AND  CHARTS  307 

two  principal  and  important  adjustments  of  the  telescope  are  the 
adjustment  of  the  eyepiece,  and  the  adjustment  for  collimation. 

To  adjust  the  eyepiece,  the  objective  should  be  turned  all  the  way 
in  or  all  the  way  out,  so  that- there  is  no  object  in  the  field.  This 
causes  a  milky  background  for  the  cross  wires.  The  eyepiece  should 
then  be  removed,  first  to  its  outer  limit  for  clearness  of  the  cross  wires, 
then  to  its  inner  limit.  The  observer  should  then  try  to  set  the  eye- 
piece at  a  point  midway  between  these  two  positions,  which  position 
should  show  the  cross  wires  very  distinctly,  and  with  exact  clearness. 

The  eyepiece,  when  once  adjusted,  should  need  no  further  atten- 
tion unless  the  observer  is  changed.  The  eyepiece  serves  to  give  a 
distinct  and  magnified  view  of  the  image.  Its  magnifying  power  is 
large,  and  its  focal  range  of  distinct  vision  is  very  small,  depending 
upon  its  magnifying  power.  With  the  ordinary  field  instruments,  it 
is  about  1/16  inch.  Both  the  image,  as  formed  by  the  objective,  and 
the  cross  wires,  should  lie  in  the  focus  of  the  eyepiece;  that  is,  they 
should  be  in  the  same  plane.  The  image  is  moved  back  and  forth  by 
moving  the  objective  in  or  out,  but  the  plane  of  the  cross  wires  is  fixed. 
If  the  two  are  brought  into  the  same  plane,  it  is  necessary  that  the 
image  be  brought  upon  the  cross  wires.  The  adjustment  just  de- 
scribed accomplishes  this  very  thing;  it  brings  the  focus  of  the  eye- 
piece on  the  cross  wires  so  they  are  most  distinct.  The  objective  may 
then  be  moved  until  the  image  or  target  also  comes  into  focus.  This 
focusing  does  not  remain  the  same  at  all  ranges,  or  for  all  observers, 
and  must  be  done  with  each  pointing,  if  the  distances  are  materially 
changed.  Should  the  image  be  not  brought  into  exact  coincidence 
with  the  cross  wires,  the  cross  wires  will  appear  to  move  slightly  on 
the  image  as  the  eye  is  moved  behind  the  eyepiece.  This  movement 
or  apparent  displacement  of  the  target  is  what  is  known  as  parallax, 
and  can  only  exist  when  the  cross  wires  do  not  lie  in  the  focus  of  the 
eyepiece.  It  is  removed  by  refocusing  the  objective,  which  moves  the 
image  until  there  is  no  perceptible  movement  of  the  wire  or  image  as 
the  eye  is  shifted.  In  other  words,  they  are  practically  in  coincidence. 
If  the  eye  were  always  in  the  center  of  the  eyepiece,  there  would  be  no 
parallax,  and  it  is  for  this  reason  that  the  eyepiece  is  covered  with  a 
shield  with  a  small  hole  in  the  center.  Even  with  this  small  hole,  a 
slight  movement  of  the  eye,  if  the  telescope  is  not  properly  adjusted, 
will  cause  a  perceptible  angular  error. 

This  adjustment  may  be  summed  up  as  follows  :  The  eyepiece 
adjustment  is  a  personal  adjustment,  and  is  made  once  for  all  for  any 
given  observer,  but  the  objective  adjustment  depends  upon  the  dis- 


308  THE  SERVICE  OF  COAST  ATILLERY 

tances  of  the  object  from  the  instrument,  and  is  made  for  each  pointing; 
that  is,  it  may  have  to  be  changed  even  for  the  same  observer  at  different 
ranges.  It  may  be  considered  as  in  perfect  focus  or  adjustment  when 
there  is  no  parallax. 

Usually  the  collimation  of  the  telescope  will  be  correct,  but  if  neces- 
sary to  adjust  it  for  collimation,  the  telescope  should  be  leveled,  and 
the  intersection  of  the  cross  wires  brought  on  the  target,  some  well- 
defined  object  being  used,  and  the  telescope  then  reversed.  That  is, 
the  telescope  is  turned  over,  so  that  what  was  the  original  top  of  the 
vertical  diameter  is  brought  to  the  bottom.  If  the  intersection  of  the 
cross  wires  is  not  then  on  the  same  part  of  the  target,  the  dew  cap  and 
ring  should  be  removed,  and  the  cross  wires  brought  on  to  the  same 
line  on  the  target  by  correcting  one-half  of  the  discrepancy  by  means 
of  the  radial  screws  in  the  object  ring.  This  operation  is  repeated  until 
the  intersection  of  the  cross  wires  remains  on  the  target  when  the  tele- 
scope is  reversed.  The  telescope -is  then  accurately  collimated.  The 
adjustment  for  parallax  should  be  made  before  collimation  is  attempted, 
as  an  error  in  parallax  will  result  in  the  adjustment  for  collimation  being 
of  no  value,  even  after  several  attempts  have  been  made  by  reversing 
the  telescope. 

Third:  For  the  proper  orientation  of  an  instrument,  it  is  essential 
that  at  least  three  datum  points  be  provided.  These  datum  points 
are  designated  D-l,  D-2  and  D-3,  the  first  being  the  short-range 
datum  point  located  between  2,000  and  2,500  yards,  the  second 
the  midrange  datum  point  located  at  about  5,000  yards,  and 
the  third  the  long-range  datum  point  at  about  9,000  yards.  Datum 
points  may  be  either  lighthouses,  buoys,  tripods  of  piles,  or  of  any 
design  suitable  in  shape  for  clear  vision  at  the  ranges  specified.  If 
cylindrical  in  shape,  they  should  be  at  least  one  foot  in  diameter  for 
every  1,000  yards  of  range  from  the  instrument,  and  sufficiently 
high  to  be  readily  distinguished  at  high  water.  Each  datum  point 
should  have  upon  it  a  reference  mark  at  a  known  height  above 
mean  low  water;  that  is,  above  the  fixed  plane  of  reference  of  the  range- 
finding  instruments.  These  heights  are  usually  from  six  to  ten  feet. 
The  datum  points  are  accurately  located,  and  their  azimuth  and  ranges 
from  the  various  stations  accurately  determined,  usually  from  their 
geodetic  position. 

Before  attemping  to  orient  the  instrument,  the  range  drum  should 
be  rotated  until  the  reading  "telescope  level"  is  opposite  the  pointer. 
The  stride  level  on  the  telescope  should  then  show  the  telescope  to  be 
horizontal.  If  this  is  not  the  case,  the  drum  should  be  rotated  until 


INSTRUMENTS,  DEVICES  AND  CHARTS  309 

that  condition  is  obtained,  the  screws  attaching  the  range  drum  to  the 
beveled  gear  should  be  loosened,  and  while  the  handle  is  firmly  held, 
the  drum  should  be  rotated  until  the  line  corresponds  with  that  on  the 
pointer,  and  the  screws  should  then  be  set  up.  The  telescope  should 
then  be  horizontal,  and  the  reading  on  the  range  drum  should  be 
"  telescope  level."  The  instrument  should  be  set  for  the  correct  height 
above  mean  low  water  by  the  height  scale.  Now  direct  the  telescope 
on  datum  point  No.  3,  the  range  drum  having  been  set  at  the  range  for 
same,  and  water-line  by  means  of  the  micrometer  screw.  Then  direct 
the  instrument  on  datum  point  No.  1,  or  the  short  range  datum  point, 
the  range  pointer  having  been  set  at  the  range  of  datum  No.  1,  and  water- 
line  by  means  of  the  height  slide  pinion.  Repeat  this  operation  until 
correct  readings  are  obtained,  by  water-lining  by  means  of  the  range 
crank.  Then  set  the  instrument  for  the  range  and  azimuth  of  the 
midrange  datum  point,  the  difference  between  the  range  reading  and 
the  true  range  as  given  in  the  datum  chart,  should  be  less  than  the  danger 
space  of  the  gun  considered  at  that  range.  If  it  is  correct,  no  further 
adjustment  should  be  made.  If  this  difference  be  appreciably  greater 
than  the  danger  space  at  the  midrange  datum  point,  then  datum  point 
Xo.  2  should  be  substituted  for  either  No.  1  or  No.  3,  and  the  set  of  ad- 
justments as  just  described  made.  Should  the  vertical  wire  not  be 
exactly  on  the  datum  point  when  set  at  the  correct  azimuth,  it  should  be 
brought  there  by  turning  the  azimuth  zero  set  screws.  This  adjust- 
ment, when  once  made,  should  be  repeated  at  longer  or  shorter  inter- 
vals, depending  on  the  extent  of  the  variation  of  the  tide,  and  when- 
ever atmospheric  conditions  have  appeared  to  change  considerably. 

The  adjustment  for  abnormal  refraction  should  always  be  made  at 
the  long-range  datum  point,  as  refraction  is  greatest  at  this  point. 
The  adjustment  for  tide  can  best  be  made  at  the  short-range  datum 
point.  The  refraction  surface  is  assumed  to  be  an  inverted  cone,  with 
its  apex  at  the  foot  of  the  vertical  base.  If  the  condition  of  refraction 
is  uniform  through  the  whole  360  degrees,  the  axis  of  this  cone  will  toe 
vertical;  otherwise,  it  will  be  inclined.  When  the  field  of  fire  is  for 
the  same  water  area,  it  is  probable  that  it  will  be  sufficiently  accurate 
to  consider  this  axis  vertical,  and  but  one  set  of  datum  points  will  be 
required. 

Use  and  Care  of  the  Instrument. — When  the  observer  is  about  to 
begin  work,  his  first  duty  is  to  verify  the  level  of  the  instrument.  He 
then  adjusts  the  eyepiece,  and  focuses  the  telescope  according  to  the 
principles  laid  down.  The  instrument  should  then  be  sighted  upon 
the  datum  points  in  the  order  given,  and  the  orientation  verified. 


310  THE  SERVICE  OF  COAST  ARTILLERY 

The  instrument  in  itself  embodies  an  automatic  means  of  correcting 
for  the  curvature  of  the  earth,  and  normal  refraction,  which  is  ordinarily 
taken  as  one-seventh  of  that  of  curvature.  When  the  range  crank  is 
rotated,  it  causes  the  rotation  of  the  range-drum  shaft  by  means  of  a 
beveled  gear.  This  rotates  the  range  drum  which  is  secured  to  the  gear, 
causes  rotation  of  the  lower  arm  of  the  lever  about  the  lever  pivots  by 
means  of  the  worm  on  the  shaft,  and  the  worm  segment  on  the  arm, 
and  causes  movement  of  the  range  pointer  by  means  of  the  worm  on 
the  shaft,  and  the  segment  on  the  pointer  arm.  The  rotation  of  the 
lower  arm  of  the  lever  causes  a  corresponding  movement  in  the  forward 
arm,  which  elevates  or  depresses  the  telescope  by  rotating  it  about  its 
trunnions.  The  rotation  of  the  pointer  arm  about  its  bearings  in  the 
pointer  bracket  is,  at  its  upper  end,  communicated  to  the  pointer,  the 
direction  of  the  movement  being  governed  by  the  guides.  If  large 
azimuth  movements  are  desired,  the  worm  box  crank  should  be  turned 
to  the  rear,  which  releases  the  cradle  so  that  it  will  freely  revolve  on 
the  spindle.  When  the  general  direction  has  been  obtained,  the  worm 
should  be  thrown  into  mesh,  and  the  movement  controlled  by  the 
azimuth  drum,  which  rotates  the  worm  and  revolves  the  cradle  about 
the  spindle  and  azimuth  circle.  If  desired,  a  small  movement  can  be 
obtained  by  loosening  the  four  azimuth  plate  bolts  and  moving  the 
table  and  all  above  it,  with  reference  to  the  base.  One  of  the  chief 
sources  of  error  in  tracking  is  due  to  the  attempt  of  the  observer  to 
follow  in  azimuth  and  range  at  the  same  time.  It  has  been  found  that 
the  best  results  are  obtained  as  follows: 

When  Using  the  Vertical  Base. — The  vessel  should  be  followed 
in  azimuth  without  attempting  to  water-line  accurately.  Keep  the 
horizontal  hair  a  little  below  the  water-line  until  the  first  stroke  of  the 
time-interval  bell,  when  the  target  should  be  accurately  water-lined 
by  bi-secting  the  bow-wave,  and  kept  accurately  water-lined  until  the 
last  stroke  of  the  bell,  at  the  same  time  maintaining  the  vertical  hair 
as  near  as  possible  on  the  designated  point  of  the  ship.  Stop  the 
instrument  promptly  at  the  last  stroke  of  the  bell  to  enable  the  reader 
to  read  the  range  and  azimuth  as  given  on  the  instrument.  If  the  vessel 
is  moving  directly  away  from  the  observer,  water-line  on  the  stern. 
If  the  bow-wave,  or  bone,  cannot  be  seen,  water-line  on  the  side  of  the 
vessel,  endeavoring  to  take  a  mean  of  the  wave  lines  which  are  made  by 
the  vessel  going  through  the  water.  It  is  not  necessary  to  water-line 
at  the  middle  point  of  the  horizontal  hair. 

It  must  be  remembered  in  using  this  system,  that  while  it  is  important 
to  make  accurate  azimuth  observations,  it  is  far  more  important  to 


PLATE   XXII 


PRISM   CASE 


EYEPIECE 
AND  ADAPTER 


TELESCOPE 
DEPRESSION  BAR 


COMPENSATING 
SCREW     

COMPENSATING 
BAR 

TANGENT 
SCREW.  NUT,  ETC. 

TABLE  CLAMP 


DRAW  TUBE 

FOCUSING  WHEEL 

TELESCOPE  TUBE 


SUN 
SHADE 


TELESCOPE 
COUNTERWEIGHT 


TABLE 


LEVELING  SCREW 


LEVELING  SCREW 
SOCKETS 


Depression  Position  Finder,  Lewis  Type. 


*"*     OF   THE 

UNIVERSITY 

OF 


INSTRUMENTS,  DEVICES  AND  CHARTS  311 

water-line  accurately,  for  in  the  vertical-base  system,  it  depends  upon 
the  accuracy  used  in  determining  the  range.  Small  errors  in  azimuth 
are  less  liable  to  occur  than  large  errors  in  range  due  to  faulty  water- 
lining.  In  attempting  to  water-line  the  side  of  the  vessel,  the  cross 
hair  is  often  lost  in  consequence  of  the  character  of  the  background. 
The  observer,  in  order  to  obtain  a  good  background,  unconsciously 
water-lines  short;  that  is,  he  will  see  a  little  water  between  the  hair 
and  the  side  of  the  ship.  The  water  passing  along  the  side  of  the 
vessel  forms  a  succession  of  waves,  and  the  observer  is  liable  to  water- 
line  over  or  under,  according  as  his  eye  catches  the  crest  or  the  bottom 
of  a  trough.  It  is  therefore  much  better  to  water-line  the  bone  whenever 
it  can  be  done. 

When  Using  the  Horizontal-Base  System. — The  vessel  should 
be  followed  in  azimjuth,  keeping  the  vertical  hair  approximately  on 
the  designated  point  until  the  first  stroke  of  the  time  interval  bell,  the 
horizontal  hair  being  at  the  same  time  kept  a  little  below  the  vessel. 
Then  bring  the  vertical  hair  accurately  to  the  designated  point,  the 
central  line  of  a  funnel  or  mast,  and  keep  it  there  until  the  last  stroke  of 
the  bell,  and  then  stop  the  instrument  promptly.  Observations  should 
be  made  on  the  forward  military  mast  whenever  the  vessel  followed 
has  one  and  it  can  be  seen.  In  other  cases,  the  observations  should  be 
made  on  the  forward  funnel  unless  the  range  officer  designates  some  other 
point.  It  is  not  well  to  use  the  bow  of  vessels  as  points  of  observa- 
tion, as  they  are  not  usually  clearly  defined,  and  in  the  horizontal-base 
system,  the  bow  may  not  always  be  visible  from  both  stations. 

Too  much  stress  cannot  be  put  upon  accuracy  in  observations, 
both  in  time  and  azimuth,  when  using  the  horizontal-base  system, 
because  upon  this  accuracy  depends  the  accuracy  of  range.  To  avoid 
error,  both  instruments  must  be  stopped  instantly  at  the  last  stroke 
of  the  bell. 

The  maximum  distance  at  which  the  depression  position  finder 
can  be  expected  to  give  sufficiently  accurate  ranges  may  be  taken 
as  a  distance  equal  to  1,000  yards  for  every  10  feet  of  height  of  the  in- 
strument above  mean  low  water.  Up  to  this  distance,  the  maximum 
allowable  error  is  one-half  of  one  per  cent,  of  the  range,  and  observers 
should  be  trained  until  they  can  accurately  and  quickly  determine 
ranges  within  the  allowable  error. 

Care  and  Preservation  of  the  Instrument. — Position  finders, 
particularly  the  telescope,  are  delicate  instruments,  and  should  not  be 
subjected  to  rough  usage,  jars  or  strains.  When  not  in  use,  the  tele- 
scope should  be  covered,  protected  from  dust  and  moisture.  To  obtain 


312  THE  SERVICE  OF  COAST  ARTILLERY 

satisfactory  vision,  the  glasses  should  be  kept  perfectly  clean  and  dry. 
A  piece  of  chamois  skin  or  a  clean  linen  handkerchief  will  always 
answer  for  cleaning  purposes,  care  being  taken  that  the  cleaning  cloth 
does  not  contain  any  dirt  or  grit.  The  lenses  will  seldom  require 
cleaning  on  the  inside,  but  when  necessary,  they  should  be  unscrewed, 
and  cleaned  by  a  competent  person  only.  The  objective  glass,  erecting 
prisms,  should  not  be  moved  from  the  objective  cell  and  ring  and  the 
prism  holder,  except  by  an  optician,  and  if  they  need  repair  they 
should  be  reported  to  the  proper  authorities.  The  cross  wires  should 
not  be  touched.  Any  dirt  should  be  removed  by  blowing.  The 
instrument  should  be  regularly .  oiled  at  all  the  marked  oil  holes  and 
bearings  with  a  high-grade  clock  oil. 

LEWIS  DEPRESSION  POSITION  FINDER,  MODEL  OF  1907 
(Plate  XXII) 

These  instruments  are  designed  to  measure  ranges  and  horizontal 
angles  of  objects  from  stations  overlooking  the  sea.  Ranges  are 
automatically  indicated  by  a  pointer  and  dial  when  the  telescope  is 
depressed  so  that  the  horizontal  cross  wire  coincides  with  the  water- 
line  of  the  object.  Horizontal  angles  are  automatically  indicated  by 
dials  when  the  vertical  cross  wire  of  the  telescope  coincides  with  the 
object 

Ranges  are  measured  in  yards,  the  dials  being  marked  for  each 
10  yards  between  the  minimum  and  maximum  ranges.  Horizontal 
angles  are  measured  to  one  hundredths  of  a  degree. 

The  principal  parts  are  the  telescope,  the  compensator  and  depres- 
sion mechanism  in  the  case,  the  azimuth  dials,  the  1/100  degree  scale, 
the  table,  body,  pedestal  cap  and  pedestal.  The  telescope  has  an 
achromatic  objective  with  a  clear  aperture  of  3  inches  and  focus  of 
25  inches,  which  affords  well-defined  flat  fields  of  view  of  3  and  2 
degrees  when  the  15-  and  25-power  eyepieces,  respectively,  are  used. 

The  range-measuring  feature  consists  in  measuring  the  tangents  of 
angles  of  depression  of  the  telescope  when  directed  at  the  water-line  of 
an  object  on  the  sea.  The  range  dial  is  spiral  in  form  and  a  traversing 
pointer  indicates  the  range  mark  to  be  read  for  any  position  of  the 
telescope.  The  graduations  on  the  range  dial  are  exact  for  one  height 
of  the  instrument,  due  allowance  being  made  for  curvature  of  the 
water  surface  and  normal  atmospheric  refraction.  This  height  is 
designated  the  initial  height  and  it  is  usually  that  height  on  the  height 
scale  which  locates  the  point  of  the  compensating  screw  in  the  sliding 


PLATE    XXIII 


Yoke  Ce.p 


Trunnion 
Clamp  Screw 


Telescope 
Trunnion 


Focusing   Knob 

Sunshade 


Objective 
Dew  Cap 


Adjusting  Screws    Slow  Motion 
Clamp 


Azimuth  Shield 
Leveling  Screws 
Instrun-.ent  Base 


Tripod 

Fhumb  Screws 


Telescope 
Lamp  and  Bracket 
Eye  Piece  Adapter 

Eye  Piece 

Eye  Lens 

Cross  Wire   Holder 

md  Adjusting  Screws 

Erecting  Prism, 

Holder  and  Case 

Reading  Openings 

Two  Way  Switch 

Worm   Box 

Adjusting  Screw 

Worm  Box 

Illuminating  Reflector 
index  Pointer  Underneath 


\V.  &  S.  Azimuth  Instrument. 


INSTRUMENTS,  DEVICES  AND  CHARTS  313 

block  at  a  distance  of  7  inches  from  the  axis  about  which  the  telescope 
rotates,  measured  horizontally  along  the  tangent-screw  rail. 

When  the  slide  block  is  set  for  this  initial  height  the  range  dial 
gives  exact  range  readings  for  all  ranges,  but  when  set  for  greater  or 
less  heights  only  the  minimum  and  maximum  ranges  will  be  correctly 
indicated.  All  intermediate  ranges  will  be  in  error  to  a  varying  ex- 
tent. By  means  of  the  compensator,  automatic  compensation  is  made 
for  these  errors,  which  are  caused  by  the  varying  effects  of  curvature 
of  the  surface  of  the  sea  and  atmospheric  refraction  when  the  instru- 
ment is  used  at  any  other  than  the  initial  height  above  sea  level. 
These  instruments  are  ma'de  for  heights  from  25  to  690  feet,  they 
have  interchangeable  depression  mechanisms,  height  scales  and  range 
dials. 

Before  using  the  instrument  the  following  adjustments  are  necessary: 

1.  To  Adjust  the  Azimuth  Mechanism. — When  moved  or  shipped 
the  azimuth  mechanism  is  put  out  of  mesh,  so  it  is  first  necessary  to  make 
this  adjustment.     On  a  radial  line  through  the  center  of  the  azimuth 
dials  are  four  screw  heads.    Counting  from  the  center  of  the  instrument 
out,  the  first  and  fourth  are  clamping  screws,  the  second  is  the  cover 
screw,  covering  the  center  of  the  unit-degree  dial,  which  can  be  removed. 
The  third  is  the  shaft  of  the  cam  which  moves  the  unit-degree  dial  into 
and  out  of  mesh  with  a  gear  on  the  body  of  the  instrument,  inside  the 
table.     To  adjust,  loosen  the  two  clamping  screws  very  slightly,  then 
turn  the  table  until  the  index  mark  nearest  the  center  of  the  instrument 
registers  with  any  one  of  the  hundreds  and  tens  of  degree  marks.     Next 
insert  a  screwdriver  in  the  slot  in  the  center  of    the  unit-degree  dial 
and  turn  it  until  zero  (0)  on  this  dial  registers  with  zero  (0)  on  the 
fixed  scale.     While  in  this  position  insert  the  screwdriver  in  the  slot 
in  the  cam  and  gently  turn  the  same  until  the  unit-degree  dial  gear 
meshes  with  the  gear  in  the  body,  and  clamp  in  this  position.     If  this 
adjustment  has  been  properly  made  the  azimuth  mechanism  will  show 
about  one-hundredth  of  a  degree  of  back  lash,  when  the  direction  of 
rotation  of  the  table  is  reversed,  and  the  table  should  turn  nearly  as 
easily  as  it  did  before  the  gears  were  meshed.     If  the  turning  of  the 
table  is  very  much  harder  than  before,  the  adjustment  should  be  re- 
peated. 

2.  To  Level. — Follow  instructions  previously  given  for  leveling. 

3.  To   Orient. — Select    some  datum  point  and  turn  the  table  by 
means  of  the  azimuth  handwheel  until  the  azimuth  of  the  datum  point 
is  indicated  on  the  azimuth  dials.     Clamp  the  table  to  the  body  of  the 
instrument  and  insert  the  large  pin  wrench  in  the  hole  in  the  side  of 


314  THE  SERVICE  OF  COAST  ARTILLERY 

the  pedestal  cap  and  turn  the  cap  until  the  vertical  cross  wire  of  the 
telescope  coincides  with  the  reference  mark  on  the  datum  point.  The 
level  of  the  instrument  should  again  be  checked  and  releveled  if  neces- 
sary. The  pedestal  cap  is  clamped  to  the  pedestal  as  soon  as  the 
adjustment  is  secured. 

4.  To  Adjust  the  Telescope. — The  telescope  adjustments  are  given 
in  detail  for  the  W.  and  S.  instruments  on  page  306,  and  are  not 
materially  different  for  this  instrument. 

To  Use  the  Instrument.  1.  Set  the  slide  block  to  the  proper  height 
of  instrument  after  deducting  the  height  of  tide  and  clamp  same  by 
means  of  the  clamping  screw. 

2.  Next  bring  the  telescope  to  bear  on  a  datum  point  about  8,000 
yards  and  turn  the  operating  nut  until  the  range  pointer  indicates  the 
correct  range  of  the  datum  point.  The  horizontal  wire  will  generally 
be  found  slightly  above  or  below  the  water  line  at  the  datum  point.  It  is 
therefore  necessary  to  bring  the  horizontal  wire  into  coincidence  by 
unclamping  the  clamp  screw  on  the  compensating  screw  and  screwing 
the  latter  up  or  down  until  the  datum  point  is  waterlined.  The  com- 
pensating screw  is  then  clamped  to  the  shaft  of  the  rack  gear.  Under 
conditions  of  normal  refraction  the  instrument  is  now  ready  for  use. 
In  practice,  however,  it  will  be  found  that  when  the  telescope  is  directed 
on  a  nearer  datum  point,  for  example  the  short  -range  datum  (2,500 
yards),  when  the  refraction  is  more  than  normal,  the  range  will  be  less 
than  2,500  yards  when  the  datum  point  is  water-lined.  So  in  order  to 
correct  for  this  abnormal  refraction  the  adjustment  must  be  made  on 
two  datum  points  (3,000  and  8,000  yards)  concurrently,  until  a  position 
of  the  sliding  block  is  found,  which  will  give  correct  range  indications 
for  the  two  datum  points.  Other  ranges  will  be  slightly  in  error,  but 
near  enough  for  all  practical  purposes. 

The  rules  for  adjustment,  use  and  care  given  above  for  depression 
position  finders  are  applicable  to  a  great  extent  to  the  azimuth  instru- 
ment and  surveyors  transit,  the  nomenclature  of  which  instruments  will 
be  found  in  Plates  XXIII  and  XXIV. 


THE   PLOTTING    BOARD 

The  principle  upon  which  all  plotting  boards  are  based  is  the  same, 
and  their  value  lies  in  the  fact  that  they  quickly  give  by  mechanical 
means  the  rate  of  travel  of  the  target,  the  range  and  azimuth  from  the 
target  to  the  directing  point  of  the  battery;  as  well  as  the  necessary 
data  for  use  on  the  Range  and  Deflection  Boards. 


PLATE    XXIV 


TELESCOPE  TUBE 

FOCUSING  SCREW 


TELESCOPE 
CLAMP  SCRE 


OBJECTIVE  AND 
OBJECTIVE  CELL 


'     EYE  PIECE 
FOCUSING  SCREW 


TELESCOPE  LEVEL 


CROSS  WIRE 
ADJUSTING  SCREW 


TELESCOPE  LEVEL 
ADJUSTING  CAPSTAN 


VERNIER 

TANGENT  SCREW 

STANDARDS 
MAGNETIC  COMPASS 


TELESCOPE 
LEVEL  SCALE 


TANGENT  SCREW 
SPRING  AND  CUSHION 


MAGNETIC  NEEDLE 
RELEASE  SCREW 


READING  OPENING 

AZIMUTH  AND  VERNIER 

SCALES 


AZIMUTH 
CLAMP  SCREW 


AZIMUTH  SLOW 
MOTION  SCREW 


SPINDLE 
COLLAR  CLAMP 


LEVELING  OR 
LOWER  PLATE 


LEVELING  SCREWS 

TRIPOD  SCREWS 

TRIPOD  LEGS 


Engineer's  Transit,  Gurley  Model. 


INSTRUMENTS,  DEVICES  AND  CHARTS  315 

The  plotting  boards  used  in  the  coast  artillery  service  are: 

Whistler-Hearn  Plotting  Board,  Model  of  1904. 

Mortar  Plotting  Board,  Model  of  1906  Mi. 

Submarine  Plotting  Board,  Model  of  1906. 

Fire  Commander's  Plotting  Board. 

The  Whistler-Hearn  Plotting  Board  is  designated  for  use  with 
a  horizontal  base  of  lengths  from  900  to  7,000  yards.  The  board  can  be 
used  as  a  right-  or  left-hand  board.  When  used  as  a  right-hand  board 
the  secondary  station  is  "on  the  right  of  the  primary  station  (where  the 
board  is  located),  the  front  being  toward  the  principal  field  of  fire. 
When  used  as  a  left-hand  board  the  secondary  station  is  on  the  left  of 
the  primary  station. 

The  plotting  board  proper,  Plate  XXV,  consists  of  a  semicircular  table 
of  well-seasoned  lumber  approximately  two  inches  thick.  The  radius  of 
the  board  is  approximately  45  inches  and  is  so  made  as  to  allow  for  ex- 
pansion and  contraction  and  to  prevent  warping.  The  diameter  plate 
is  a  heavy  piece  of  brass  7  inches  wide  and  J-inch  thick  and  is  attached 
to  the  under  side  of  the  board  by  bolts  which  pass  through  slotted  holes 
to  allow  for  expansion  and  contraction  of  the  board. 

The  base-line  arm  is  made  of  bronze  and  extends  the  whole  diameter 
of  the  board  on  its  upper  surface,  and  when  set  at  zero  it  is  parallel  to 
the  diameter  plate.  The  main  azimuth  circle  extends  around  the  curved 
surface  of  the  table  and  is  greater  than  a  semicircle ;  it  is  made  of  bronze 
in  several  pieces  and  is  put  together  in  two  layers,  the  pieces  of  the  upper 
layer  breaking  joints  with  the  lower  portion,  thus  forming  a  complete 
metallic  strip.  The  middle  of  the  top  portion  of  the  circle  is  counter- 
sunk to  admit  the  insertion  of  a  piece  of  zinc  upon  which  the  degrees 
are  numbered.  The  outer  edge  is  notched  with  V-shaped  notches  about 
J  of  an  inch  deep,  each  notch  corresponding  to  one  degree  in  azimuth. 
The  entire  azimuth  circle  is  bolted  at  its  two  extremities  to  the  diameter 
plate;  all  measurements  therefore  made  on  the  board,  whether  angular 
or  linear,  are  independent  of  the  table  proper,  the  expansion  or  contrac- 
tion of  the  wood  does  not  in  any  way  effect  the  accuracy  of  the  board. 

The  station  blocks  are  mounted  on  the  base-line  arm.  One  block, 
known  as  the  primary  block,  is  attached  to  the  base-line  arm  and  fits 
over  the  main  pintle  center;  the  other  block,  known  as  the  secondary 
block,  is  attached  to  the  base-line  arm,  but  is  arranged  so  that  it  will 
move  laterally  along  the  base-line  arm  and  may  be  set  for  any  length  of 
base  line  on  either  side  of  the  main  center  or  primary  (station)  block. 
Each  block  is  provided  with  a  pivot  or  center  over  which  the  primary 
arm,  secondary  arm  and  auxiliary  arm  are  pivoted. 


316  THE  SERVICE  OF  COAST  ARTILLERY 

The  primary  arm  is  a  scale  arm  or  alidade  which  is  pivoted  at  the  main 
center,  carried  by  the  primary  block.  This  arm  is  made  of  brass,  steel 
or  copper,  and  is  graduated  on  one  edge  to  the  scale  of  300  yards  to  the 
inch,  the  graduations  representing  yards  in  range,  the  smallest  reading 
being  10  yards.  The  secondary  arm  is  a  similar  scale  arm  and  is  pivoted 
at  the  center  on  the  secondary  block;  it  is  likewise  graduated  for  range 
to  the  scale  of  300  yards  to  the  inch,  the  smallest  reading  being  10  yards. 

The  auxiliary  arm  is  a  similar  arm  but  without  graduations,  and  is 
pivoted  at  the  main  center  or  at  the  same  point  on  the  primary  block 
as  the  primary  arm. 

The  connecting  bar  or  coupler  is  a  brass  piece  connecting  the  outer 
ends  of  the  secondary  and  auxiliary  arms;  its  length  depends  upon  the 
length  of  the  base  line  for  the  board  considered,  that  is,  the  coupler 
would  be  equal  to  the  length  of  the  base  line  in  inches  at  the  scale  of 
the  board.  The  primary  and  auxiliary  arms  are  fitted  with  an  index 
box  which  slides  and  may  be  locked  on  the  azimuth  circle.  The  index 
box  consists  of  the  box  proper  which  moves  on  the  azimuth  circle  and 
is  fitted  with  a  lock  called  the  degree  lock  by  means  of  which  the  box 
may  be  located  and  locked  at  any  particular  degree.  The  scale  arms 
pass  through  the  boxes  and  by  means  of  a  rack  and  pinion  may  be 
moved  in  either  direction  through  an  arc  of  .99  of  a  degree ;  the  pinion 
attached  to  the  box  is  actuated  by  a  dial  plate  or  index  disk  and  knob. 
The  dial  is  graduated  in  one  hundred  parts  and  on  its  outer  edge  are 
one  hundred  teeth;  it  is  arranged  so  that  one  revolution  of  the  dial 
plate  carries  either  arm  through  .99  of  a  degree.  The  dial  is  held 
and  locked  in  any  desired  position  by  a  dial  lock  or  index  disk  clamp 
which  fits  into  the  teeth  on  the  circumference  of  the  dial  and  prevents 
the  movement  of  the  arm  when  locked. 

Over  the  center  of  the  primary  block  is  mounted  the  gun  center ,  which 
consists  of  two  slides,  the  lateral  adjusting  slide  and  the  longitudinal  ad- 
justing slide;  the  gun  arm  (See Plate XX VI) , the  fixed  limb, the  movable 
limb,  the  correction  box,  the  degree  tally,  and  the  hundredths  dial. 
The  lateral  slide  has  a  motion  along  the  base-line  arm,  it  is  dovetailed 
on  a  guide  piece  attached  to  the  base-line  arm,  and  can  be  clamped  in 
any  position  by  means-  of  three  set  screws  on  the  rear  side  which  act 
against  a  long  gib.  The  guidepiece  is  graduated  and  the  slide  is  fitted 
to  a  vernier  reading  to  one  yard.  When  this  vernier  is  set  at  zero  the 
center  line  of  the  slide  passes  through  the  main  center  of  the  board. 
The  longitudinal  slide  is  fitted  into  the  lateral  slide  so  that  it  may  be 
moved  in  a  direction  at  right  angles  to  the  base-line  arm.  On  the  longi- 
tudinal slide  is  a  scale  and  on  the  lateral  slide  a  vernier  by  means  of 


INSTRUMENTS,  DEVICES  AND  CHARTS  317 

which  the  slide  may  be  set  as  desired ;  the  longitudinal  slide  carries  the 
gun-arm  center. 

When  the  vernier  on  the  lateral  slide  is  at  zero  the  gun-arm  center 
is  on  the  base  line.  When  the  longitudinal  and  lateral  slide  are  both 
set  at  zero  the  gun-arm  center  is  directly  over  the  main  center  of  the 
board  or  the  center  at  which  the  primary  arm  is  pivoted.  The  longi- 
tudinal slide  is  held  in  position  by  two  set  screws  which  act  against  short 
gibs;  the  lateral  and  longitudinal  slides  are  provided  so  that  the  gun- 
arm  center  may  be  located  at  such  a  point  on  the  board  with  reference 
to  the  main  center  as  to  correspond  to  the  location  of  the  directing  gun 
or  point  of  a  battery,  to  the  scale  of  the  board,  and  that  of  the  primary 
station  of  the  battery. 

The  gun  arm  is  made  of  German  silver  or  aluminium.  It  is  a  scale 
arm  or  alidade  pivoted  at  the  gun  center,  and  is  used  to  determine  the 
range  and  azimuth  of  the  target  from  the  directing  point  of  a  battery. 
The  gun-arm  center  consists  of  the  gun-arm  proper,  the  fixed  limb,  the 
movable  limb  and  the  correction  box  (and,  in  the  first  type  of  board, 
the  travel  scale) . 

The  fixed  limb  is  a  semicircular  metallic  piece  attached  to  the 
longitudinal  adjusting  slide  by  three  screws.  This  limb  carries 
the  degree  index  of  the  gun-arm  azimuth  circle,  and  the  index  or  dial 
for  reading  the  fractions  of  a  degree.  The  gun-arm  pintle,  about  which 
the  azimuth  circle  and  correction  box  revolve,  is  attached  to  this  limb. 

The  movable  limb  is  an  azimuth  circle.  It  has  geared  teeth  on  its 
outer  edge  which  mesh  into  the  pinion  which  actuates  the  mechanism 
of  the  hundredths  dial.  The  degrees  are  graduated  on  the  brass  circle, 
but  are  numbered  on  a  strip  of  zinc.  This  limb  is  centered  on  the  gun- 
arm  pintle. 

The  correction  box  is  a  device  for  mechanically  making  the  range 
corrections  for  atmospheric  conditions  and  travel  as  determined  from 
the  range  board,  and  also  for  making,  mechanically,  the  deflection  cor- 
rections as  determined  from  the  deflection  board.  The  range  corrections 
are  made  by  sliding  the  gun  arm  in  or  out  the  required  distance  which 
is  measured  by  a  range  difference  scale  on  the  arm.  This  scale  is  seen 
through  a  reading  opening,  or  window,  in  the  box.  The  arm  is  moved 
in  or  out  by  a  rack  and  pinion.  The  deflection  corrections  are  made  by 
moving  the  box  through  a  given  azimuth  angle  indicated  by  a  scale  on 
the  box.  The  box  is  actuated  by  a  worm  gear  which  is  attached  to  the 
movable  limb. 

The  degree  tally  is  a  device  for  indicating  the  angular  travel  of  the 
target  during  a  predicting  interval,  and  is  on  the  left  of  the  window 


318  THE  SERVICE  OF  COAST  ARTILLERY 

of  the  gun-arm  azimuth  circle.  Over  the  face  of  the  dial  moves  a  hand, 
the  reading  of  which  gives  the  angular  travel  in  degrees.  The  frac- 
tions of  a  degree  are  read  from  the  outer  graduations  of  the  hundredths 
dial  of  the  gun  arm.  The  tally  scale  is  marked  in  reference  numbers, 
running  from  0  to  30,  the  origin,  or  zero,  being  15. 

The  travel  scale  is  a  sliding  scale  on  the  gun  arm  used  in  determining 
the  change  in  the  range  of  the  target  during  the  observing  interval  on 
boards  where  the  range  board  has  not  been  provided  with  the  new  travel 
scales.  At  the  center  of  this  scale  is  a  pointer  which  is  set  at  the  in- 
dicated range  of  the  target  at  the  end  of  an  observing  interval.  At  the 
end  of  the  next  observing  interval,  by  turning  down  the  leaf,  the  change 
in  range  for  the  interval  will  be  indicated  by  reference  numbers.  The 
leaf  is  held  up  at  all  other  times  by  a  spring,  so  as  not  to  interfere  with 
readings  of  the  range  scale. 

The  gun-arm  shoe  is  made  of  bronze,  and  is  used  to  facilitate  the  use 
of  the  gun  arm  by  obviating  the  necessity  for  raising  it,  and  also  prevents 
the  bending  of  the  other  arms.  It  slides  along  the  gun  arm,  and  is  held 
in  position  by  a  friction  spring. 

To  Set  Up  the  Board. — The  trestles  should  be  set  up,  and  the  board 
placed  on  them  in  a  horizontal  position,  with  the  diametrical  spider  arm 
of  the  board  resting  on  the  oakum-reinforced  pieces  of  the  trestle.  Care 
should  be  exercised  in  mounting  the  board  and  removing  it  from  its 
box,  as  the  azimuth  circle  has  been  carefully  adjusted  to  the  base  line 
arm  and  primary  center,  and  a  blow  on  the  azimuth  circle  or  the  base- 
line arm  may  destroy  the  adjustment  of  the  entire  board. 

The  direction  and  length  of  the  base  line  having  been  determined, 
loosen  the  screws  holding  the  proper  end  of  the  base-line  arm,  and  slip 
the  sliding  station  block  on  the  base-line  arm.  The  screws  on  the  end 
of  the  base-line  arm  should  then  be  replaced  and  tightened.  The  small 
gib  of  the  sliding  block  should  be  slipped  into  place,  and  the  vernier 
attached.  The  small  gib  in  the  rear  of  the  secondary  station  block 
should  be  loosened  sufficiently  to  adjust  for  the  correct  length  of  reading 
for  the  base  line  in  yards.  After  this  adjustment  is  made,  the  gib  screw 
should  be  carefully  tightened.  An  adjustment  of  one  degree  in  azimuth 
in  either  direction  can  be  given  to  the  base  line,  but  ,50  of  a  degree 
is  the  maximum  amount  necessary  to  be  used. 

To  make  this  adjustment,  slacken  the  clamp  screws  at  each  end  of  the 
base-line  arm,  and  also  the  screw  directly  on  the  end  of  the  primary 
station  block.  Set  to  the  correct  position  by  means  of  the  vernier. 
This  caution  is  given  owing  to  the  fact  that  on  account  of  the  length  of 
the  base-line  arm  there  is  apt  to  be  some  spring  which  might  give  a  false 


INSTRUMENTS,  DEVICES  AND  CHARTS  319 

position  with  only  one  reading.  Both  verniers  should  be  read  and 
should  agree.  The  readings,  however,  should  be  in  opposite  directions. 
Two  supporting  plates  with  two  dowel  pins  in  each  are  placed  under 
each  end  of  the  base-line  arm  to  support  it  and  prevent  sagging.  It  is 
not  necessary  to  remove  these  in  making  an  adjustment  of  the  base-line 
arm. 

The  primary  arm  for  right-handed  base  line  is  marked  with  the 
initials  "P.  R."  The  secondary  arm  for  the  same  board  would  be 
marked  "S.  R.,"  and  the  gun  arm  "G.  R."  The  auxiliary  arm  is  simply 
marked  "R.,"  on  one  side,  and  "L.,';  on  the  other  side. 

For  a  left-handed  plotting  board  the  primary  arm  would  be  marked 
"P.  L.",  the  secondary  arm  "S.  L."  and  the  gun  arm  "G.  L."  The 
"R"  side  of  the  auxiliary  arm  is  up  for  a  right-handed  board,  and  the 
"  L"  side  is  up  for  a  left-handed  board.  When  mounting  the  scale  arms, 
the  primary  arms  should  be  placed  next  to  the  board  being  pivoted  on 
the  main  pintle.  The  auxiliary  arm  is  pivoted  on  the  same  pintle  and 
placed  on  top  of  the  primary  arm.  The  secondary  arm  passes  over  the 
primary,  and  is  connected  to  the  auxiliary  arm  by  a  coupler  which  has 
the  same  length  as  the  base  line.  The  object  of  the  coupler  is  to  keep 
the  secondary  arm  parallel  to  the  auxiliary  arm,  and  obviate  the  neces- 
sity of  having  more  than  one  azimuth  circle,  as  the  auxiliary  arm  is 
pivoted  at  the  center  of  the  main  azimuth  circle,  or  at  the  pintle  center 
of  the  board. 

The  azimuth  readings  from  the  secondary  station  being  set  by  means 
of  the  index  box  on  the  auxiliary  arm,  the  coupler  keeping  the  second- 
ary arm  parallel  with  said  arm,  must  necessarily  give  the  secondary  arm 
the  correct  direction  with  reference  to  the  primary,  or  in  other  words, 
set  the  secondary  arm  at  the  same  azimuth. 

Two  index  boxes  are  furnished  with  each  board,  one  for  the  auxiliary 
arm  and  one  for  the  primary  arm.  These  boxes  are  marked  "  Aux.  R." 
and  "Prim.  L."  and  the  other  is  marked  "Aux.  L."  and  "Prim.  R."  For 
a  right-handed  base  line  the  index  boxes  marked  "  Aux.  R."  is  for  the 
auxiliary  arm,  and  the  box  marked  "  Prim.  R."  is  for  the  primary  arm. 
If  a  left-handed  board  is  used,  the  box  marked  "Aux.  L."  is  for  the 
auxiliary  arm,  and  the  box  marked  "  Prim.  L."  is  for  the  primary  arm. 

To  assemble  the  index  boxes,  set  the  pointer  at  50,  and  insert  the 
rack  in  position  according  to  the  corresponding  marks  A  or  B,  being 
careful  to  see  that  the  teeth  of  the  pinion  0  meshes  with  the  teeth  of  the 
rack  marked  0.  The  rack  should  be  held  in  position  until  the  index 
box  is  placed  over  the  scale  arm.  Bring  the  arm  on  which  the  index 
box  is  to  be  mounted  over  one  of  the  places  near  either  end  of  the  base- 


320  THE  SERVICE  OF  COAST  ARTILLERY 

line  arm,  where  the  azimuth  circle  is  cut  out.  If  a  right-handed  base 
line  is  used,  the  primary  index  box  is  inserted  over  the  azimuth  circle 
at  the  right-hand  end  of  the  base  line,  and  the  auxiliary  arm  is  inserted 
at  the  left-hand  end  of  the  base  line,  and  vice  versa  for  a  left-handed 
base  line. 

Be  sure  to  hold  the  rack  in  position  while  the  scale  arm  is  being  in- 
serted under  the  rack  and  between  the  locking  plate  and  the  index  box. 
The  scale  arms  must  not  be  lifted  too  high  when  assembling  the  boxes,  as 
the  arms  may  be  bent  at  the  pivots.  If  the  rack  has  been  inserted  cor- 
rectly, the  pointer  of  the  dial  will  move  clockwise  from  0  to  99. 

On  the  outside  of  each  index  box,  on  the  locking  plate,  will  be  noticed 
a  small  brass  lip.  When  the  edge  of  this  lip  is  opposite  the  center  of  the 
notch  in  the  azimuth  circle,  the  locking  lever  can  be  pulled  out,  thus 
locking  the  index  box  to  the  azimuth  circle  and  permitting  an  adjust- 
ment up  to  .99  of  a  degree  by  moving  the  index  disk  on  the  index  box. 
Above  the  locking  plate  is  a  small  latch,  and  before  attempting  to  turn 
the  index  disk,  this  latch  must  be  pulled  out.  The  movement  of  this 
knob  is  only  about  one-eighth  of  an  inch,  and  does  not  require  a  heavy 
strain.  After  the  correct  reading  has  been  obtained  by  setting  the  disk, 
this  latch  is  pushed  in  and  locks  the  disk  in  position. 

To  mount  the  gun-arm  center,  place  it  over  the  tongue  of  the  base-line 
arm  with  the  dials  of  the  gun-arm  center,  toward  the  rear  of  the  board. 
Insert  the  lateral  adjusting-slide  gib  according  to  the  corresponding 
marks  on  the  gib  and  gun-arm  center.  Then  screw  up  the  gib  screw 
slightly,  so  that  the  gun-arm  center  can  slide  by  the  primary  or  secondary 
station  blocks,  but  not  so  tight  that  the  gun  arm  cannot  be  moved. 

To  set  the  gun-arm  center,  the  fixed  limb  must  be  moved  to  expose 
the  scales  on  the  longitudinal  adjusting  slide.  The  fixed  limb  is  secured 
to  the  longitudinal  adjusting  slide  by  three  retaining  screws  and  the 
gun-arm  center  pivot.  One  retaining  screw  is  located  in  the  rear  position 
of  the  gun-arm  azimuth  subscale,  and  is  entered  by  removing  the  tally 
subdial.  Two  screws  are  also  located  on  either  side  of  the  pivot,  and  are 
entered  from  the  top  of  the  fixed  limb  by  turning  the  gun  arm  to  the 
left.  The  right  end  retaining  screw  near  the  pivot  can  be  taken  out, 
and  similarly  by  turning  the  gun  arm  to  the  right,  the  left  end  retaining 
screw  can  be  taken  out.  The  fixed  limb  can  then  be  turned  to  the  right 
or  left  about  the  gun-arm  center  pivot.  The  position  of  the  gun-arm 
center  is  set  according  to  the  distance  in  yards  of  the  gun  in  front  of, 
or  in  rear  of  the  base  line.  This  adjustment  is  made  on  the  longitudinal 
adjusting  slide,  which  has  two  scales  on  it,  of  25-yard  divisions,  and 
two  verniers  attached  to  enable  readings  to  one  yard.  The  two  gib 


THE 

UNIVERSITY 


INSTRUMENTS,  DEVICES   AND  CHARTS  321 

screws   on   the   left-hand   side    and    under  the   fixed   limb,   are    then 
tightened. 

The  limit  of  this  adjustment  is  1,000  yards  to  the  front  or  to  the  rear 
of  the  base  line.  The  distance  in  yards  to  the  right  or  left  of  the  primary 
station  is  set  on  the  lateral  adjusting  slide,  which  also  has  a  vernier 
reading  to  one  yard,  with  two  scales  each  of  25-yard  divisions.  The 
limit  of  this  adjustment  is  4,000  yards  to  the  right  or  left  of  the  primary 
station.  The  three  gib  screws  on  the  rear  of  the  lateral  adjusting  slides 
are  then  tightened.  After  the  position  of  the  gun-arm  center  has  been 
located,  the  fixed  limb  should  be  replaced.  The  "targ  "  is  for  the  pur- 
pose of  obtaining  an  exact  reading  at  the  intersection  of  the  edges  o 
the  primary  and  secondary  arms.  It  should  be  held  up  against  the  edge 
of  the  secondary  arm,  and  moved  along  that  edge  until  it  touches  the 
primary.  This  gives  the  intersection.  Care  should  be  taken  not  to 
bring  it  against  the  edge  of  the  primary  arm  with  too  great  a  force  and 
thus  injure  the  edge  of  the  arm. 

To  Orient  the  Board. — The  normal  line  of  the  board  is  the  radius  at 
right  angles  to  the  base-line  arm,  when  the  verniers  at  each  end  of  the 
base-line  arm  are  set  at  0.  The  center  of  the  center  notch  in  the  azimuth 
circle  and  the  center  of  the  main  pintle,  establish  this  normal.  As  has 
been  stated,  the  base-line  arm  may  be  moved  through  one  degree4 
either  way,  and  to  set  the  proper  reading  by  means  of  verniers  attached 
to  each  end. 

The  0  of  the  base-line  arm  may  be  given  any  convenient  degree  num- 
ber, depending  upon  the  azimuth  of  the  actual  base  line.  It  is  con- 
venient to  number  one  0  with  the  nearest  degree  to  the  back  azimuth; 
that  is,  180  degrees  plus  the  azimuth  of  the  base  line.  For  example: 
Assume  that  the  azimuth  of  the  base  line  is  312.26  degrees,  and  that 
the  base  line  is  left-handed.  Then  the  0  at  the  left  hand  of  the  base 
line  arm  would  be  numbered  312  degrees,  and  the  0  at  the  right-hand 
end  would  be  numbered  132  degrees.  To  orient  the  base-line  arm  to 
correspond  with  the  actual  base,  it  is  necessary  to  swing  the  base-line 
arm  clockwise  to  0.26  degrees.  That  is,  to  set  the  left  end  to 
312.26  degrees.  The  other  of  course  would  be  set  at  132.26  degrees. 
Assume  that  the  azimuth  of  the  base  line  was  312.90  degrees,  then  the 
left  end  would  be  numbered  313  degrees,  and  the  right  end  133  degrees. 
To  set  the  base  line  at  312.90  it  would  be  necessary  to  swing  the  base- 
line arm  contraclockwise  through  0.10  degrees;  in  other  words,  the 
left-hand  end  is  to  be  set  at  312.90  degrees,  and  the  right-hand  end 
at  133.90  degrees. 

To  orient  the  gun-arm  center,  bring  the  gun-arm  center  over  the 


322  THE  SERVICE  OF  COAST  ARTILLERY 

primary  center  by  placing  the  zeros  of  the  longitudinal  adjusting  slide 
verniers  and  the  lateral  adjusting  slide  verniers  coincident  with  the 
zeros  of  their  respective  scales.  See  that  the  0  of  the  worm  guard  is 
opposite  15  on  the  azimuth  correction  scale,  and  the  scale  on  the  microm- 
eter head  of  the  worm  is  at  0.  Bring  the  "primary  arm  to  the  normal 
line  of  the  board,  and  be  sure  that  the  pointer  of  the  index  box  on  the 
primary  arm  is  set  at  0.  Place  the  targ  against  the  reading  edge  of  the 
primary  arm,  and  bring  the  gun  arm  carefully  up  against  the  targ.  If 
properly  done,  the  reading  edges  of  the  primary  and  gun  arm  will  now 
coincide  to  the  normal  line  of  the  board.  Set  the  azimuth  pointer  at 
the  gun-arm  azimuth  window  by  means  of  the  adjusting  screw  to  the 
whole  degree  of  the  azimuth  of  the 'normal. 

Next  set  the  gun-arm  azimuth  sub-dial  indicator  to  0  by  loosening 
the  screw  holding  the  indicator  in  place.  This  will  allow  an  adjustment 
of  J,  J  or  j  of  a  degree.  If  that  is  not  sufficient,  the  tally  sub-dial  is 
removed.  The  vernier  dial  face  can  now  be  adjusted  within  the  limits 
of  1-  of  one  degree  by  loosening  the  retaining  screw  and  moving  the  dial 
until  the  pointer  is  at  0. 

To  test  this  orientation  the  gun  arm  should  be  moved  away  from  the 
targ,  and  brought  up  to  it  several  times.  The  gun-arm  center  is  now 
moved  to  a  position  on  the  board  to  a  corresponding  position  of  the  gun 
as  previously  explained.  To  test  the  accuracy  of  the  board,  take  three 
positions  of  a  target  near  the  center  of  the  board  and  extremes  respec- 
tively, each  at  about  a  range  of  6,000  yards,  and  calculate  trigonomet- 
rically  and  see  if  the  calculations  agree  with  the  readings  given  by 
the  board. 

Another  simple  test  of  the  accuracy  of  a  plotting  board  is  to  plot  the 
location  of  the  datum  points  with  a  range  and  azimuth  of  either  station, 
and  then  check  the  range  and  azimuth  as  given  by  the  board  from  the 
other  station.  The  azimuth  and  range  found  should  agree  with  that 
given  on  the  datum  sheet. 

Care  of  the  Board. — Too  much  attention  cannot  be  given  to  the  scale 
arms,  as  the  accuracy  of  the  board  depends  upon  the  reading  edges  being 
true,  straight  edges,  and  any  roughness  due  to  handling  of  these  arms 
will  impair  the  accuracy  of  the  board.  If  the  scale  on  the  micrometer 
head  of  the  worm  needs  adjustment,  it  should  be  made  by  using  the 
spanner  wrench  and  pin  wrench  furnished  for  loosening  the  jam  nut. 
If  the  worm  has  any  backlash,  this  will  be  due  either  to  the  fact  that  the 
worm  is  not  in  close  enough  mesh,  or  that  the  screw  at  the  left-hand  of 
the  worm  is  not  adjusted  properly.  To  correct  the  first,  release  the 
two  clamp  screws  on  the  worm,  and  move  the  worm  forward  to  the  proper 


INSTRUMENTS,  DEVICES  AND  CHARTS  323 

mesh;  then  tighten  the  screws.  To  correct  the  second  error,  release  the 
jam  nut  by  using  the  small  end  of  the  spanner  wrench,  and  then  adjust 
the  screw  by  holding  the  screw  with  the  small  pin  wrench,  and  tighten 
the  jam  nut.  All  the  pivot  bearings  should  be  oiled  regularly,  and  the 
board  kept  free  from  dust  at  all  times.  When  not  in  use,  the  index  box 
locking  levers  should  be  left  released. 

To  Use  the  Board. — The  gun  plotting  board  is  used  for  batteries  of 
the  primary  armament  and  of  the  intermediate  armament  to  include 
6-inch  batteries  provided  with  a  separate  base  line. 

Readings  are  taken  simultaneously  at  the  base-end  stations  and  trans- 
mitted to  the  arm-setters  for  the  primary  and  secondary  arms  of  the 
plotting  board.  The  arm-setters  lock  the  index  box  in  the  degree  notch 
of  the  azimuth  called  to  them  by  the  readers  over  their  respective  tele- 
phones, locking  the  box  in  this  position  with  the  degree  lock.  They 
then  set  the  index  disk  of  the  box  to  the  hundredths  of  degrees  as  called 
and  lock  the  index  disk  with  the  index  clamp.  When  this  operation  is 
completed  each  arm-setter  calls  "  set,"  which  is  a  signal  for  the  plotter 
to  move  the  "  targ  "  along  the  left  edge  of  the  secondary  arm  until  it 
comes  to  the  intersection  of  the  secondary  and  primary  arms,  which 
point  indicates  the  position  of  the  target. 

After  the  first  two  readings  the  plotter  moves  the  gun  arm  up  to  this 
intersection  and  reads  and  transmits  the  range  as  indicated  on  the  gun 
arm  to  the  guns.  These  readings  are  sent  to  the  guns  every  15  seconds 
and  are  the  corrected  ranges  for  the  target  being  tracked. 

The  corrections  are  made  as  follows:  The  assistant  plotter  at  the  first 
setting  of  the  gun  arm  turns  the  hundredths  dial  for  gun  arm  until  the 
'zero  is  opposite  the  pointer  and  also  sets  the  degree  tally  so  that  the 
number  15  of  the  degree  tally  scale  is  opposite  the  pointer.  At  the  sec- 
ond setting  of  the  gun  arm  he  calls  off  the  reference  number  from  the 
degree  tally  and  the  hundredths  dial  of  the  gun  arm.  This  reference 
number  indicates  the  angular  travel  of  the  target  during  the  observing 
interval  and  is  used  by  the  deflection  computer  in  the  operation  of  the 
deflection  board.  The  assistant  plotter  also  sets  the  wind  component 
indicator  to  the  proper  azimuth  which  is  taken  from  the  azimuth  circle 
for  the  gun  arm. 

In  Case  III  the  assistant  plotter  calls  off  the  corrected  azimuth  as 
shown  on  the  azimuth  circle  for  gun  arm  and  index  for  hundredths  of 
degree  scale. 

The  range  correction  device  is  set  at  the  proper  reference  number  as 
obtained  from  the  range  board  by  the  range-correction  computer. 


324  THE  SERVICE  OF  COAST  ARTILLERY 

MORTAR   PLOTTING    BOARD,    MODEL    OF    1906 

(See  Plate  XXVII.) 

This  board  is  similar  to  the  Whistler-Hearn  plotting  board  just  de- 
scribed, the  principal  difference  being  the  mortar  arm,  and  mortar  arm 
center.  The  two  principal  parts  of  the  mortar  arm,  which,  are  shown 
in  detail  in  Fig.  48,  are  the  range  and  zone  scales. 

The  range  scale  gives  the  range  of  the  object  plotted  from  the  mortar, 
and  in  conjunction  with  the  mortar-arm  center  gives  its  azimuth.  The 
zone  scale  is  in  8  zones,  and  gives  the  elevation  in  degrees  and  the  times 
of  flight  in  seconds  for  all  ranges  from  2,000  to  12,000  yards.  The  zone 
scale  permits  of  adjustment  for  correction.  The  mortar  arm  is  pivoted 
to  the  mortar-arm  center  by  means  of  the  mortar-arm  box,  and  permits 
of  it  being  raised  from  the  board  at  any  time  in  a  vertical  plane.  On 
account  of  the  increased  size  of  the  mortar-arm  center  over  the  gun-arm 
center  of  the  regular  plotting  board,  a  mortar-center  support  has  been 
provided.  The  instructions  for  adjusting,  assembling  and  orienting  the 
Whistler-Hearn  plotting  board  hold  good  in  the  case  of  this  board. 

To  Use  the  Board. — The  mortar-plotting  board  is  used  similarly  to 
that  of  the  gun-plotting  board  except  that  the  mortar  arm  is  provided 
with  a  sliding  scale,  as  shown  in  Plate  XXVII,  which  is  graduated  into 
degrees  of  elevations  and  times  of  flight  for  each  zone.  The  two  arm- 
setters  on  hearing  the  azimuth  at  the  signal  for  each  observation  set 
and  lock  the  primary  and  secondary  arms  as  previously  described  for 
the  gun-plotting  board.  The  plotter,  as  soon  as  he  hears  the  command 
"set,"  marks  the  position  of  the  target  by  making  a  pencil  mark  on 
the  plotting-board  chart  at  the  intersection  of  the  two  arms. 

The  tracking  of  the  target  is  commenced  and  four  or  more  positions 
plotted  on  the  board  at  20-second  intervals.  The  plotter  then  moves 
the  mortar  arm  up  to  the  last  plotted  position  of  the  20-second  readings 
and  estimates  where  the  vessel  will  be,  providing  the  course  is  continued 
for  two  minutes  ahead  of  the  time  of  the  last  plotted  point.  He  calls 
out  the  zone  indicated  on  the  mortar  arm  to  the  azimuth  computer,  who 
operates  the  mortar  deflection  board,  and  who  in  turn  transmits  these 
data  to  the  booths. 

The  plotter  also  notes  and  remembers  the  time  of  flight  indicated  for 
the  range  and  zone  in  question.  The  position  of  the  target  is  then 
plotted  either  every  30  seconds  or  every  minute.  For  example,  it  will 
be  assumed  that  it  is  plotted  every  minute.'  In  the  cut,  Fig.  49,  the  first 
four  plotted  positions  at  20-second  intervals  are  indicated  by  the  num- 


INSTRUMENTS,  DEVICES  AND  CHARTS 
Times  of '  r/ig^jt  £/e> 

tvvW^Vv/^ 


325- 


Zone  n  umber 


i    « 1  Normal 


Mo\seabfe    G 


FIG.  48. 


326  THE  SERVICE  OF  COAST  ARTILLERY 

bers  1,  2,  3  and  4.  The  position  of  the  target  one  -minute  after  the 
plotted  position  No.  4  is  indicated  at  5.  When  this  point  is  obtained 
the  plotter  sets  the  leg  of  the  predicter  nearest  to  him  at  position  4 
and  the  next  leg  to  the  position  5.  The  third  leg  will  then  indicate  the 
predicted  point,  and  assuming  the  time  of  flight  to  be  50  seconds,  the 
leg  of  the  predicter  marked  50  will  indicate  the  set-forward  point.  When 
the  plotter  has  obtained  these  points  the  mortar  arm  is  brought  up  to 
the  set-forward  point  and  the  elevation  read  from  the  arm.  No.  1,  the 
assistant  plotter,  also  calls  out  the  azimuth  of  the  set-forward  point  to 
No.  4  or  the  operator  of  the  mortar-deflection  board.  The  plotter  then 
moves  the  mortar  arm  up  to  the  predicted  point  indicated  by  position  6 
and  calls  out  the  range  to  the  assistant  plotter,  who  transmits  this  range 


Sef  Forward  Point^  ^-Predicted  Point 

FIG.  49. — Mortar  Predicter. 

to  the  battery  commander's  station  to  be  used  in  case  relocation  is 
necessary.  The  assistant  plotter  also  transmits  to  the  battery  com- 
mander's station  the  azimuth  of  the  predicted  point.  The  range  and 
azimuth  as  read  by  the  plotter  and  assistant  plotter  are  the  range  and 
azimuth  of  the  directing  point  of  the  battery.  Should  this  point  not 
correspond  with  the  position  of  the  battery  commander's  station,  it  is 
necessary  for  the  battery  commander  to  use  these  data  to  relocate  from  the 
directing  point  of  the  battery  to  the  position  his  instrument  occupies. 
The  operator  at  the  deflection  board  uses  the  data  called  to  him  by  the 
plotter  and  assistant  plotter,  as  follows: 

He  first  sets  the  cylinder  of  the  deflection  board,  shown  in  Plate 
XXVIII  so  that  the  whole  degrees  of  azimuth  as  read  to  him  by  the 
assistant  plotter  appear  in  the  slit  of  the  drum.  He  then  moves  the 


INSTRUMENTS,  DEVICES  AND  CHARTS 


327 


pointer,  which  is  carried  on  the  drift-scale  slide  and  used  for  reading  the 
azimuth  subscale,  to  the  hundredth  of  the  azimuth  read  by  the  assistant 
plotter.  He  next  transmits  to  the  booth  the  elevation  called  to  him  by 
the  plotter  and  at  the  same  time  sets  the  small  pointer  (elevation  pointer) 
on  the  deflection  scale  to  the  elevation  given  him  by  the  plotter.  In  case 
110  arbitrary  correction  has  resulted  from  the  observation  of  fire,  the  large 
pointer  on  the  deflection  scale  then  indicates  the  corrected  azimuth  of 
the  set-forward  point  and  No.  4  transmits  this  azimuth  to  the  booths 
as  soon  as  he  has  completed  the  operations  just  described.  The  zone 
number,  elevation,  and  corrected  azimuth  are  posted  from  the  booths 
so  that  the  mortars  may  be  laid  on  the  data  given.  The  battery  com- 
mander relocates  from  the  directing  point  of  the  battery  for  the  position 
of  his  instrument  and  sets. his  instrument  at  the  relocated  azimuth  as 
determined  from  the  range  and  azimuth  of  the  predicted  point  pre- 
viously transmitted  to  the  station  by,  the  assistant  plotter.  As  the  target 
comes  on  to  the  vertical  wire  of  his  instrument  he  signals  or  closes  the 
switch  for  firing  the  mortar  or  mortars  of  the  pits  that  have  signaled 
"  ready."  Should  the  target  not  come  on^to  the  vertical  wire  of  the 
battery  commander's  instrument  at  the  proper  time,  he  withholds  the 
fire  and  gives  instructions  to  "  relay." 


ZONES    AND    VELOCITIES 

The  number  of  zones,  muzzle  velocities  corresponding  thereto,  zone 
limits,  width  of  zones  and  oven-laps  for  the  12-inch  mortar,  cast-iron, 
steel-hooped,  and  the  12-inch  mortar,  steel,  are  shown  in  the  following 
table: 


g 
£ 

*c 

c 

z 

12-inch  Mortar,  Cast-iron,  Steel-hooped. 

12-inch  Mortar,  Steel. 

Muzzle 
Veloc- 
ity. 
F.S. 

Weight 
of  Pro- 
jectile. 
Lbs. 

rj                 Width 
Zone                 , 

Limits-         Zone. 
Yds.            Yds. 

Over- 
laps. 

Yds. 

Muzzle 
Veloc- 
ity. 
F  8. 

Weight 
of  Pro- 
jectile. 
Lbs. 

Zone 
Limits. 

Yds. 

Width 
of 
Zone. 

Yds. 

Over- 
laps. 

Yds. 

1 

560 

1046 

2225-3000      775 

400 

550 

1046 

2210-2970 

760 

370 

2 

610 

1046 

2600-3480      880 

480 

600 

1046 

2600-3431 

831 

361 

3 

670 

1046 

3080-4110    1030 

400 

660 

1046 

3070-4030 

960 

399 

4 

743 

1046 

3710-5000    1290 

400 

725 

1046 

3631-4800 

1169 

371 

5 

837 

1046  '4600-6240    1640 

400 

810 

1046 

4429-5940 

1511 

420 

6 

910 

1046 

5840-7319    1479 

594 

915 

1046 

5520-7476 

1956 

449 

7 

1050 

824 

6725-9225    2500 

1050 

1046 

7027-9250 

2223 

492 

8 

1300 

824 

8758- 

3261 

12019 

328  THE  SERVICE  OF  COAST  ARTILLERY 

In  target  practice  with  12-inch  mortars  the  extreme  zones  in  which 
practice  may  be  held  will  be  the  sixth  with  the  cast-iron  steel-hooped 
mortar,  and  the  fifth  with  the  steel  mortar,  except  that  with  the  steel 
mortar  mounted  upon  the  model  of  1896  Mil  carriage  or  the  model  of 
1896  carriage  converted  to  the  model  of  1896  Mi  carriage,  practice  may 
be  held  in  all  zones. 


MORTAR   PLOTTING   BOARD,    MODEL    OF  1906  Mi 

This  is  a  special  plotting  board,  made  for  cases  where  the  mortar-arm 
center  is  more  than  1,000  yards  behind  the  base-line.  The  maximum 
distance  permitted  for  the  mortar-arm  center  to  be  behind  the  base  line 
arm  in  this  type  of  board  is  2,000  yards.  In  order  to  meet  this  require- 
ment, the  lateral  adjusting  slide  of  the  board  has  been  extended  towards 
the  rear,  and  the  base-line  arm  moved  back.  The  mortar  arm  has  also 
been  changed  to  correspond  with  the  other  changes  on  this  type  of 
board. 

SUBMARINE    PLOTTING    BOARD,    MODEL  OF    1906 

This  board  is  the  Whistler-Hearn  plotting  board,  model  of  1904,  sim- 
plified. The  board  is  not  provided  with  a  gun  arm  or  gun  center.  The 
scale  of  the  board  is  100  yards  to  the  inch,  or  in  some  cases,  150  yards 
to  the  inch,  depending  upon  the  mine  field  to  be  plotted.  The  primary 
arm,  secondary  arm,  base-line  arm  and  base-line  verniers  are  slightly 
different  in  construction  from  the  regular  plotting  board,  but  tha 
principles  of  the  board  are  exactly  the  same. 

Due  to  the  fact  that  the  range  of  the  board  is  necessarily  limited,  the 
scale  on  the  arms  has  been  changed  to  100  yards  to  the  inch,  or  150 
yards  to  the  inch.  The  board,  when  assembled,  adjusted  and  oriented, 
has  mounted  upon  the  table  a  chart  showing  the  location  of  the  principal 
datum  points  within  the  mine  field,  the  outline  of  the  entrance  to  the 
harbor,  the  various  channels,  the  depths  of  water  passable  by  the  various 
types  of  battle-ships,  cruisers  and  torpedo  boats,  and  also  the  location 
of  the  distribution  boxes  and  the  mines  comprising  the  mine  field. 

To  Use  the  Board. — Readings  are  taken  at  the  base-end  stations  of  the 
mine-base  line  simultaneously,  every  15  seconds,  and  the  primary  and 
secondary  arms  set  at  the  azimuth  readings  sent  is  by  the  readers  at  the 
base-end  stations;  each  arm-setter  indicating  by  calling  the  word  "set" 
when  his  arm  is  set  at  the  azimuth  called  to  him  by  the  reader  at  the 
primary  or  secondary  instrument. 


INSTRUMENTS,  DEVICES  AND  CHARTS 


At  this  signal  the  plotter  indicates 
the  position  of  the  target  at  the  inter- 
section of  the  two  arms  by  making  a 
dot  with  the  point  of  a  pencil.  The 
target  is  tracked  in  this  manner  until 
its  position  is  indicated  to  be  within 
the  predicting  distance  of  any  mine  of 
the  group  over  which  the  vessel  will 
pass;  this  distance  ordinarily  is  taken 
as  1J  times  the  distance  traveled  by 
the  target  during  any  observing  inter- 
val. At  the  last  stroke  of  the  time- 
interval  bell  which  would  give  such  a 
position  the  plotter  starts  a  stopwatch, 
and  after  the  arm-setters  have  set  their 
arms  to  the  readings  sent  them,  the 
plotter  calls  out  "  arms  off,",  at  which 
command  the  arm  setters  move  the 
primary  and  secondary  arms  out  of 
the  plotter's  way. 

The  plotter  then,  with  the  mine- 
prediction  ruler,  measures  the  distance 
from  the  last  plotted  point  to  the  mine, 
and  from  the  last  plotted  point  to  the 
preceding  plotted  position  of  the  tar- 
get, obtaining  in  the  first  case  the  dis- 
tance the  vessel  has  to  travel  before 
crossing  the  particular  mine  in  ques- 
tion, and  in  the  second,  the  travel  of 
the  target  during  the  predicting  inter- 
val. He  then  manipulates  the  mine- 
prediction  ruler  shown  in  Fig.  50,  and 
obtains  the  time  that  it  will  take  the 
vessel  to  travel  from  the  last  plotted 
point  to  the  mine. 

Previously  the  plotter  has  sent 
word  to  the  casemate  the  number  of 
the  group  and  the  number  of  the 
mine  in  the  group  that  the  target,  if  it 
continues  its  course,  will  pass  over 
or  nearest  to.  At  a  short  interval 


/JT 


TIME  IN  15 


5— 


e— 


YARDS 


5ECOM&-2S 


25— 


YA/WS 
TO 


/s— 


20  — 


/oo — 


//o  — 


—  30 


—75 


S3S 


60 


Stefe 


.250 
£=2.70 


o — = 
o    — 


O       _Z 


_ 

0 


FIG.  50. 


330 


THE  SERVICE  OF  COAST  ARTILLERY 


before  the  time  required  for  the  vessel  to  travel  from  the  last  plotted 
point  to  the  mine  has  expired  (say  two  seconds),  which  is  allowed  for 
transmission  of  message  from  the  mine  primary  station  to  the  mining 
casemate,  the  plotter  calls  out  "  ready,  fire."  This  method  of  plotting 
is  that  used  for  judgment  firing.  The  mine-plotting  board  is  not  pro- 
vided with  the  gun  center  or  gun  arm.  It  can  be  used  for  either  the 
horizontal  or  vertical  base  system,  exactly  the  same  way  as  the  gun- 
plotting  board. 


FIRE  COMMANDER'S  PLOTTING  BOARD 

The  Fire  Commander's  plotting  board  is  the  regular  Whistler-Hearn 
plotting  board,  with  a  pantograph  attachment,  as  shown  in  Fig.  51,  to 

f 

tCB 


FIG.  51. 


enable  the  Fire  Commander  to  adapt  his  board  to  any  base  line  of  the 
fire  command. 

The  scale  of  the  board  is  300  yards  to  the  inch.  The  pantograph  arms 
are  so  constructed  that  when  pivoted  at  the  pantograph  pivot  the  stylus 
moves  through  a  reverse  space  five  times  greater  than  that  moved 


INSTRUMENTS,  DEVICES  AND  CHARTS  331 

through  by  the  end  connected  to  the  longitudinal  slide.  Hence,  the 
scale  of  the  templet  is  five  times  the  scale  of  the  board,  or  60  yards  to 
the  inch.  The  holes  in  the  templet  represent  an  accurate  reversed  plan 
of  the  centers  of  the  observation  stations,  and  directing  guns  of  the 
various  batteries  of  the  fire  command  considered.  The  names  of  these 
stations  and  batteries  are  marked  directly  under  their  respective  holes 
on  the  templet.  If  the  pantograph  arms  are  moved  so  that  the  stylus 
can  be  placed  in  the  hole  representing  the  primary  or  center  pivot  of 
the  board,  the  gun  center  will  be  exactly  over  the  primary  center  of  the 
board.  As  the  line  through  the  two  holes  on  the  templet  is  parallel 
to  the  base  line,  it  is  obvious  that  as  the  stylus  is  moved  forward  or 
backward,  right  or  left,  the  gun  center  or  its  longitudinal  ordinate 
will  move  reversely  backward  or  forward,  and  will  move  reversely 
the  lateral  ordinate,  left  or  right,  a  distance  one-fifth  of  that  covered 
by  the  reversed  corresponding  motion  of  the  stylus  over  the 
templet.  Hence,  if  the 'stylus  is  inserted  in  any  of  the  holes  in  the  tem- 
plet, it  will  place  the  gun  center  in  a  position  exactly  corresponding  to 
the  particular  hole  used,  relative  to  the  base  line,  and  the  range  and 
azimuth  as  read  to  any  plotted  point  will  be  the  correct  range  and 
azimuth  of  that  point  from  the  station  or  directing  gun  designated  by 
''the  marking  of  the  hole  in  the  templet  occupied  by  the  stylus. 
Moving  the  gun  center  to  the  various  positions  it  may  occupy  does 
not  change  the  orientation  of  the  gun-azimuth  dial,  as  the  movement 
to  obtain  the  various  positions  are  broken  up  into  components  parallel 
to  and  normal  to  the  base  line. 

In  making  range  corrections,  the  clamping  lever  should  be  released 
and  the  required  adjustment  made  by  moving  the  range  dial.  The  gun 
arm  is  at  zero  when  the  range-dial  pointer  indicates  the  reference 
number  2,000. 

In  making  azimuth  corrections,  release  the  knurled  clamping  screw 
on  the  azimuth-correction  plate.  By  turning  the  azimuth-correction 
worm,  the  correct  adjustment  can  be  made.  Read  degrees  directly 
from  the  azimuth-correction  plate,  and  one  one-hundredths  of  degrees 
from  the  micrometer  drawn  on  the  right-hand  end  of  the  worm. 

The  azimuth-correction  plate  is  at  zero  when  the  line  on  the  worm 
cover  coincides  with  the  reference  number  15.  The  micrometer  drum 
should  then  be  at  "  0."  If  the  micrometer  drum  needs  adjusting,  re- 
lease the  clamping  nut  by  the  spanner  wrench  to  be  found  in  the  drawer. 
Hold  the  micrometer  down  in  position  with  small  pin  to  be  found  in 
drawer,  and  tighten  the  nut.  If  the  worm  works  too  freely  in  its  bearings, 
it  may  be  adjusted  by  the  set  screw  and  nut  on  the  left  of  the  worm 


332  THE  SERVICE  OF  COAST  ARTILLERY 

bracket.  If  the  worm  has  any  back  lash,  it  may  be  taken  up  by  re- 
leasing the  two  screws  clamping  the  bracket  to  the  fixed  limb,  and  by 
setting  the  bracket  closer  to  the  azimuth  correction  plate. 

The  small  dial  to  the  left  of  the  gun-azimuth  dial  is  called  the  tally 
dial,  and  in  conjunction  with  the  tally  sub-dial,  is  used  for  obtaining 
angular  travel  of  a  target  during  a  predicting  interval. .  The  hand  scale 
is  a  sliding  scale  and  is  intersected  in  an  undercut  groove  on  the  gun  arm. 
It  is  used  for  obtaining  change  in  range  of  a  target  during  an  observing 
interval. 

Should  the  lateral  and  longitudinal  slides  become  loose,  due  to  wear, 
they  may  be  adjusted  by  the  adjusting,  wedge  on  each  slide.  To  do  this, 
first  take  out  hexagonal  screw  attaching  the  pantograph  to  the  longi- 
tudinal slide.  Then  by  releasing  the  screw  on  the  small  end  of  the  ad- 
justing wedge.,  the  screw  on  the  large  end  may  be  adjusted  until  the 
slide  can  be  moved  freely,  but  without  side  play.  The  screw  on  the 
small  end  of  the  wedge  is  then  tightened,  thereby  clamping  the  wedge. 
It  is  imperative  that  the  pantograph  be  disconnected  from  the  longi- 
tudinal slide  before  attempting  to  adjust  either  slide,  as  each  must  be 
tested  separately,  and  as  there  would  be  danger  of  bending  the  stylus 
end  of  the  pantograph  in  moving  the  gun  center,  if  either  slide  is  made 
too  tight. 

The  assembling,  adjustments  and  orientation  of  the  board  are  similar 
in  all  respects  to  those  of  the  regular  Whistler-Hearn  plotting  board. 

THE  RANGE  BOARD 

The  range  board  is  a  device  by  means  of  which  the  range  corrections 
for  atmospheric  conditions;  range  corrections  for  tide;  range  corrections  for 
travel  of  target;  and  range  corrections  for  variation  in  muzzle  velocity  are 
mechanically  added  and  subtracted. 

The  total  range  correction,  when  determined,  is  applied  to  the  range- 
correction  scale  on  the  gun  arm  of  the  plotting  board. 

The  nomenclature  of  the  board  is  shown  in  Plate  XXIX,  and  consists 
of  &  frame  in  which  a  graphic  range-correction  chart  is  mounted.  In  front 
of  the  chart  is  a  balanced  horizontal  ruler  which  can  be  moved  up  or 
down  and  set  opposite  any  range  on  the  chart.  The  vertical  scale  of  the 
chart  is  marked  in  both  range  and  time  of  flight.  The  ruler  is  main- 
tained in  position  by  chains  secured  to  it  at  each  end  which  pass  over 
chain  sprockets  and  are  secured  to  a  counterweight  which  balances  the 
ruler.  A  clamp,  or  clamping  screw  on  the  left  of  the  frame  secures  the 
ruler  at  any  desired  position. 


Of   THE 

f   UNIVERSITY  j 

OF 


INSTRUMENTS,  DEVICES  AND   CHARTS  333 

On  the  ruler  is  a  scale  for  the  ruler,  a  bar  and  a  pointer.  The  scale  is 
fixed  in  position  on  the  plate  of  the  ruler,  while  the  bar  and  pointer  are 
arranged  to  slide  horizontally.  The  scale,  bar,  and  pointer,  in  connec- 
tion with  the  chart,  constitute  the  computing  device  for  mechanically 
adding  algebraically  the  various  corrections.  The  scale  on  the  ruler  and 
the  horizontal  scale  on  the  chart  is  100  yards  to  the  inch. 

The  origin  of  the  correction  scale  of  the  gun  arm  on  the  plotting  board 
in  numbered  2,000,  in  order  that  the  correction  to  be  made  thereon  shall 
never  be  negative.  This  requires  2,000  to  be  taken  as  the  origin  of  the 
scale  on  the  ruler. 

The  curves  on  the  chart  indicate  the  magnitude  of  the  corrections  to 
be  added  or  subtracted,  and  the  ruler  mechanically  performs  the  addition 
or  subtraction.  In  each  set  of  curves  the  horizontal  distance  from  any 
curve  to  the  normal  of  the  set  (which  is  the  heavy  vertical  line  in  the 
center  of  each  set  of  curves),  is  equal  to  the  correction  in  yards  of  range 
at  the  particular  range  considered,  corresponding  to  the  conditions  repre- 
sented by  the  curve,  plotted  to  the  scale  of  100  yards  to  the  inch.  The 
curves  are  drawn  for  every  2  per  cent,  variation  in  the  density  of  the  air, 
for  evory  10  foot-seconds  of  muzzle  velocity;  for  every  5  feet  of  tide, 
and  for  every  10  miles  of  wind.  For  conditions  when  the  values  lie  be- 
tween these  least  readings,  the  pointer  can  be  set  by  the  eye  closely 
enough  for  all  practical  purposes. 

The  vertical  scale  of  the  chart  has  a  time  of  flight  scale,  one  second  to 
the  inch.  Each  range  number  is  plotted  at  a  point  corresponding  to  the 
time  of  flight  for  that  particular  range. 

The  travel  device  consists  of  a  travel  scale,  secured  by  two  supports 
on  the  top  of  the  box;  the  upper  ends  of  the  supports  pass  through  the 
top  of  the  box,  are  threaded  and  provided  with  nuts.  To  adjust  the 
position  of  the  scale  the  top  edge  of  each  should  be  about  27  inches  above 
the  zero  line  of  the  chart.  A  travel  bar  is  arranged  along  the  travel 
scale,  and  carries  a  trammel  or  pointer  for  reading  the  upper  scale, 
also  a  trammel  or  pointer  for  reading  the  lower  scale;  these  are  so 
arranged  as  to  slide  freely  along  the  travel  bar.  The  pointer  for  the 
lower  reading  is  so  arranged  as  to  obscure  the  upper  row  of  graduations 
on  the  travel  scale. 

The  normal  of  the  travel  scale  is  300  and  this  scale  is  graduated  from 
the  normal  to  the  right  with  10-yard  divisions  to  a  reading  of  109,  and 
to  the  left  with  10-yard  divisions  to  600,  which  number  is  taken  as  a 
new  origin  for  graduations  on  a  second  scale  from  0  to  900.  The  first- 
described  scale  is  the  travel  scale  used  for  determining  the  travel  of  the 
target  during  the  predicting  interval;  the  second  scale  is  a  tally  scale 


334  THE  SERVICE  OF  COAST  ARTILLERY 

used  to  determine  the  change  in  range  of  the  target  during  the  predicting 
interval. 

The  travel  device  is  so  located  that  the  normal  is  directly  over  the 
normal  of  the  prediction  scale  on  the  chart,  which  is  also  marked  300. 
The  upper  row  of  graduations  on  the  travel  scale  correspond  to  a  fifteen- 
second  observing  interval  and  the  lower  row  to  a  thirty-second  observing 
interval.  Near  the  right-hand  end  of  the  travel  bar  is  an  index  mark, 
and  a  string  is  attached  at  this  point.  This  string  passes  over  the  travel 
scale,  through  the  hole  in  the  centering  stud,  and  around  the  hook  eye 
to  the  eye  pin.  A  rubber  band  is  tied  to  the  lower  end  of  the  string  to 
keep  it  taut  as  the  travel  bar  is  moved  back  and  forth.  When  the  index 
of  the  travel  bar  is  set  at  normal  the  string  should  be  over  the  normal 
of  the  prediction  curves  on  the  chart,  that  is  over  the  300-line  mark. 
The  travel  scale  for  a  15-second  time  interval  is  so  graduated  that  if  the 
string  is  set  for  any  reference  number  thereon,  it  will  intersect  the  hori- 
zontal line  corresponding  to  15-second  time  of  flight  at  a  distance  from 
the  normal  equal  to  the  travel  represented  by  the  number  on  the  scale 
at  which  the  string  is  set.  The  scale  for  a  30-second  time  interval  is  so 
constructed  that  under  the  same  conditions  the  string  will  intersect  the 
horizontal  line  corresponding  to  15-second  time  of  flight  at  one-half 
this  distance. 

The  left  end  of  the  travel  scale  is  graduated  from  right  to  left  in  ranges 
from  0  to  1,600;  only  the  numbers  from  1,000  up  are  marked  on  the  scale 
without  the  digit  indicating  the  thousands.  This  is  so  that  the  scale 
may  be  adapted  to  any  range,  the  proper  thousand  number  in  any 
particular  case  being  understood  or  assumed. 

Across  the  box,  near  the  top  of  the  board,  is  a  bar  for  curve  indicators 
or  pointers,  on  which  are  four  curve  pointers,  which  admit  of  sliding  back 
and  forth.  They  are  used  to  mark  the  particular  curve  which  is  to  be 
used  in  making  corrections. 

Near  the  lower  edge  of  the  ruler  is  the  bar  for  the  tally  indicator,  on 
which  the  tally  indicator  slides  back  and  forth.  This  is  used  to 
indicate  the  amount  of  the  total  range  correction  in  the  last  previous 
operation  of  the  board. 

To  avoid  the  use  of  two  sets  of  numbers  of  the  same 
magnitude  with  plus  and  minus  signs,  reference  numbers  are 
used  for  denoting  the  various  curves  on  the  chart.  For  example:  If 
the  wind  curves  are  numbered  in  both  directions  from  0,  there  would 
be  a  plus  10-mile  wind  curve,  and  a  minus  10-mile  wind  curve,  and 
it  would  require  extreme  care  to  avoid  the  wrong  curve  being  used,  so 
in  using  reference  numbers,  the  normal,  or  0,  is  taken  as  50,  in  which 


INSTRUMENTS,  DEVICES  AND  CHARTS  335 

case  the  reference  numbers  for  a  plus  and  minus  10-mile  wind 
become  40  and  60  respectively,  and  in  this  way  liability  of  error  is  re- 
duced. With  the  atmosphere  curves,  it  is  reasonable  to  assume  that  the 

<\f 

maximum  variation  that  is  ever  liable  to  occur  in  the  value  of  --   is 

o 

16  per  cent.  The  normal  of  these  curves  is  therefore  taken  as  16,  and 
the  reference  numbers  run  from  0  to  32,  and  read  from  left  to  right. 
With  the  wind  curves,  the  board  is  constructed  for  a  50-mile  plus  or 
minus  wind;  therefore,  the  normal  is  numbered  50,  and  the  reference 
numbers  run  from  0  to  100,  and  read  from  left  to  right.  The  reference 
numbers  for  the  tide  curves  represent  the  actual  height  of  tide  in  feet, 
plus  or  minus,  likewise  the  velocity  curves  are  numbered  with  the  actual 
velocity  to  which  they  correspond*.  The  travel  and  prediction  curves 
consist  of  parallel  vertical  lines.  The  travel  curves  consist  of  the 
graduations  on  the  travel  scale  of  the  travel  device,  and  the  prediction 
curves  are  the  parallel  vertical  lines  on  the  chart,  the  horizontal  scale 
of  which  is  100  yards  to  the  inch.  In  this  set  of  curves  the  300  yards 
is  taken  as  the  normal,  and  for  convenience  in  computation,  the  refer- 
ence numbers  of  the  travel  scale  read  from  100  to  500,  from  right  to 
left,  while  the  reference  numbers  of  the  prediction  scale,  which  is  also 
graduated  from  100  to  500,  read  from  left  to  right. 

Adjustment. — Before  using  the  board,  it  is  important  to  see  that  the 
chart  has  been  properly  mounted  and  in  the  correct  position.  The  0  line 
on  the  print  should  be  on  the  line  with  the  upper  eyelets,  and  the  300- 
yard  line  on  the  chart  should  be  in  line  with  the  two  eyelets  at  the  right. 
The  brass  eyelets  are  placed  on  the  left  side  as  well  as  the  right  side  of 
the  canvas  chart  mount  so  that  the  back  side  of  the  canvas  chart  mount 
may  be  used  for  the  chart  for  one  pounder  sub-caliber  guns. 

To  Use  the  Board. — The  curve  indicators  or  markers  are  first  set  on 
the  proper  reference  numbers  for  each  set  of  curves.  The  tide-curve 
marker  is  set  to  the  tide  given  on  the  tide  dial  of  the  aeroscope  indicator, 
shown  in  Fig.  53.  The  marker  for  the  atmosphere  curve  is  set  at  the 
reference  number  indicated  on  the  aeroscope  dial,  giving  the  atmosphere 
density  per  cent.  The  velocity  curve  is  set  at  the  velocity  obtained 
from  the  trial  shots,  or  that  assumed  for  the  series  of  firings.  The  wind 
curve  is  set  at  the  reference  number  obtained  from  the  wind  component 
indicator,  shown  in  Fig.  52. 

The  travel  bar  is  moved  until  the  string  is  at  normal  (300) ,  and  the 
pointer  set  at  the  last  three  numbers  of  the  first  range  called  off  by  the 
plotter.  When  the  second  range  is  called  off,  the  travel  bar  is  moved 
until  the  pointer  indicates  the  last  three  numbers  of  that  range.  The 


336  THE  SERVICE  OF  COAST  ARTILLERY 

string  is  now  set  to  indicate  the  travel  during  any  time  of  flight.  The 
ruler  is  then  set  at  the  first  range  called  off  by  the  plotter.  The 
scale  bar  for  the  ruler  is  set  at  normal  (2,000).  The  board  is  now 
arranged  for  making  the  corrections  for  the  first  range  called  off  by 
the  plotter. 

The  pointer  is  then  set  to  the  curve  indicated  by  the  curve  marker  for 
tide,  and  the  bar  moved  until  the  pointer  is  on  the  normal  line  of  the 
curves.  The  difference  in  the  reading  on  the  scale  on  the  ruler  between 
2,000  and  the  reading  shown  would  indicate  the  total  correction  due  to 
tide.  In  the  same  manner  the  corrections  are  made  for  atmosphere, 
velocity,  and  wind,  and  finally  for  travel,  which  is  made  as  follows:  The 
pointer  is  set  on  the  string  after  the  latter  has  been  set  fdr  a  particular 
travel;  the  bar  is  then  moved  until  the  pointer  is  on  the  normal.  The 
distance  through  which  the  index  is  moved  will  be  that  corresponding  to 
the  time  of  flight  for  the  range  at  which  the  ruler  is  set. 

If  the  pointer  is  again  set  on  the  prediction  scale  at  a  distance  from 
the  normal  equal  to  the  travel  during  the  time  interval,  as  indicated  by 
the  setting  of  the  string  on  the  travel  scale,  and  the  bar  is  again  moved 
until  the  pointer  is  opposite  the  normal,  the  index  will  then  have  added 
or  subtracted  the  travel  during  one  time  interval.  This  is  necessary  in 
that  it  requires  that  there  shall  be  added  to  or  subtracted  from  the  range 
corrections  for  any  range  a  correction  which  is  equal  to  the  travel  of  a 
target  during  the  time  of  flight  plus  the  travel  during  the  time  interval. 
In  order  to  do  this  by  one  operation  the  reference  numbers  of  the  pre- 
diction scale  are  made  to  read  in  the  opposite  direction  from  those  on  the 
travel  scale,  as  the  travel  away  from  the  gun  requires  an  additive  motion 
of  the  bar. 

The  numbers  on  the  travel  scale  read  from  right  to  left,  while  the 
numbers  on  the  prediction  scale  read  from  left  to  right,  so  that  after 
setting  the  pointer  opposite  the  string,  it  will  be  possible  by  moving  the 
bar  in  a  direction  to  make  the  pointer  pass  the  normal  until  it  is  opposite 
the  numerical  value  of  the  travel  during  the  time  interval  to  combine  the 
two  corrections  in  one  operation. 

After  these  corrections  have  been  made  the  scale  on  the  ruler,  as  in- 
dicated by  the  index  on  the  bar,  indicates  the  reading  to  which  the  gun 
arm  should  be  set  and  thus  automatically  changes  the  actual  range  to 
that  of  the  corrected  range  which  is  sent  to  the  gun.  For  a  better  under- 
standing of  the  board  it  might  be  well  to  explain  that  if  the  index  of  the 
bar  is  set  at  the  origin  of  the  scale,  2,000,  and  the  pointer  thereon  is  set 
on  any  curve  and  then  the  bar  is  moved  to  right  or  left  until  the  pointer 
is  opposite  the  normal  of  that  particular  set  of  curves  it  is  apparent  that 


INSTRUMENTS,  DEVICES  AND  CHARTS  337 

the  index  will  be  moved  along  the  scale  bar  of  the  ruler  a  distance  to 
scale  equal  to  the  distance  between  the  curve  and  the  normal. 

The  index  will  then  indicate  a  number  on  the  scale  equal  to  2,000,  plus 
or  minus  the  correction  corresponding  to  the  curve  used.  That  is,  if  the 
trammel  is  set  to  the  left  of  the  normal,  and  the  bar  is  moved  until  the 
trammel  is  opposite  the  normal,  the  bar  will  move  to  the  right,  and  as  the 
scale  bar  for  ruler  reads  from  left  to  right,  the  reading  of  the  index  will 
then  be  greater  than  2,000,  and  therefore  the  correction  is  an  additive 
one.  For  example:  If  the  atmosphere  is  heavy,  it  requires  an  additive 
range  correction,  as  the  projectile  would  fall  short.  Therefore  the  0  of 
the  atmosphere  curve,  which  represents  16  per  cent,  increase  in  the 
weight  of  the  air,  and  the  32  curve  a  16  per  cent,  decrease  in  the  weight 
of  the  air,  and  the  16  curve  represents  standard  weight  of  air.  Further, 
a  slight  wind  would  require  an  additive  range  correction  in  order  to  over- 
come its  retarding  effect  on  the  projectile;  therefore,  the  0  of  the  wind 
curve  represents  a  50-mile  per  hour  head-wind  component.  The  100- 
mile  wind  curve  represents  a  50-mile  per  hour  rear-wind  component,  and 
the  reference  number  50  represents  a  0-wind  component  for  range. 

On  the  side  of  the  board  opposite  to  the  regular  chart  used  for  guns, 
is  a  chart  used  with  sub-caliber  tubes,  which  is  constructed  100  yards  to 
the  inch.  In  order  to  use  this  chart  with  the  plotting  board,  the  normal 
of  the  range-correction  scale  of  the  gun  arm,  and  the  ruler  of  the  range 
board  is  taken  as  2,400,  and  a  paper  scale,  300  yards  to  the  inch,  is  pasted 
on  the  gun  arm  showing  ranges  from  1,400  to  3,500  yards.  When  the 
index  reading  of  the  range  board  is  beyond  the  limits  of  the  correction 
scale  on  the  gun  arm,  the  gun  arm  may  be  set  by  applying  the  following 
rule :  If  the  reading  be  between  2,500  and  3,500,  subtract  1,000  from  the 
reading  and  set  the  arm  accordingly,  and  add  1,000  to  the  range.  For  a 
reading  over  3,500  subtract  2,000  and  add  2,000  to  the  range.  To  a 
reading  between  500  and  1,500,  add  1,000  and  subtract  1,000  from  the 
range.  To  readings  less  than  500,  add  2,000  and  subtract  2,000  from 
the  range. 

The  range-correction  computer  sets  the  range-correction  scale  on  the 
gun-arm  center  to  the  reading  obtained  from  the  scale  on  the  ruler. 

The  range  boards  issued  prior  to  December,  1906,  have  curves  con- 
structed to  give  the  corrections  for  the  actual  range.  Those  issued  after 
December,  1906,  have  curves  constructed  to  give  the  corrections  for  the 
corrected  ranges  instead  of  the  actual  ranges. 


338  THE  SERVICE  OF  COAST  ARTILLERY 


THE    DEFLECTION    BOARD     (GUN) 

The  deflection  board  is  a  machine  by  means  of  which  the  corrections 
for  travel  in  azimuth  during 'the  observing  interval,  corrections  for  travel  in 
azimuth  during  the  time  of  flight,  corrections  for  wind,  and  corrections  for 
drift,  are  mechanically  computed. 

In  Case  III  the  total  azimuth  corrections  obtained  are  applied  to  the 
azimuth  correction  device  on  the  plotting  board. 

In  Cases  I  and  II  the  total  deflection  correction  is  sent  to  the  guns  and 
set  off  on  the  deflection  scales  of  the  telescopic  sights. 

The  nomenclature  of  the  board  is  shown  in  Plate  XXX,  and  consists 
of  a  base,  upon  which  slides  a  movable  frame  called  the  platen.  This  frame 
slides  on  a  rod,  to  which  it  is  attached  by  means  of  two  trammels.  On 
the  left-hand  trammel  there  is  a  set  screw  by  means  of  which  the  platen 
may  be  locked  to  the  rod.  The  rod  in  turn  is  attached  to  the  base  by 
two  brackets.  In  the  left  bracket  is  a  threaded  sleeve  which  can  be 
turned  by  a  milled  head  screw  or  worm  wheel  near  it,  which  gives  a  slow 
motion  to  the  rod  and  consequently  to  the  platen. 

Attached  to  the  base  at  the  lower  side  are  three  scales,  namely,  the 
deflection  scale,  the  travel  scale,  and  the  azimuth  correction  scale.  On  the 
latest  type  of  boards,  the  travel  scale  is  not  provided,  and  is  no  longer 
needed  for  use  on  the  board.  The  first  two  scales  are  fixed  on  the  base, 
and  the  other  is  movable. 

On  the  left-hand  side  and  attached  to  the  base,  is  the  wind  arm  and 
the  wind  arc.  Attached  to  the  platen  is  the  platen  (travel)  scale,  "over 
which  moves  a  travel  arm.  The  platen  scale  can  be  given  two  positions 
on  the  platen;  one  corresponding  to  a  time  interval  of  15  seconds,  and 
one  corresponding  to  a  time  interval  of  20  seconds. 

The  T  square  moves  over  all  and  slides  on  the  rod.  On  the  face  of  the 
T  square  is  a  range  scale,  called  the  T-square  scale.  Attached  to  the  left 
side  of  the  platen  is  a  piece  of  metal  called  the  leaf.  The  curved  edge  of 
the  leaf  has  a  drift  curve,  which  is  used  for  setting  the  platen  for  drift. 
On  the  leaf  is  a  range  scale  which  is  used  in  setting  the  platen  for  wind 
and  drift,  this  is  called  the  leaf-range  scale. 

The  platen  scale  represents  the  travel  in  azimuth ;  its  graduations 
represent  degrees  and  hundredths  on  a  scale  of  half  of  a  degree  to  the 
inch.  It  is  numbered  from  left  to  right  and  the  number  at  the  origin  is 
15  degrees.  This  is  a  reference  number  to  correspond  to  the  azimuth 
degree-tally  dial  on  the  plotting  board.  The  deflection  scale  indicates 
the  deflection  to  be  set  off  on  the  sight  in  Cases  I  and  II,  the  scale  being 


^SAR?' 

OF   THE 

UNIVERSITY 


OF 


INSTRUMENTS,  DEVICES  AND  CHARTS  339 

constructed  to  J  of  a  degree  per  inch;  it  is  numbered  from  left  to  right 
with  3  degrees  in  the  center;  this  is  also  a  reference  number,  made  to 
correspond  with  a  similar  reference  number  on  the  deflection  scale  of 
the  sight. 

The  azimuth  correction  scale  indicates  the  correction  to  be  applied  to 
the  gun  arm  on  the  plotting  board  when  Case  III  is  used;  the  scale  is 
constructed  to  \  of  a  degree  per  inch,  and  is  numbered  from  left  to  right 
with  15  degrees  in  the  center,  this  being  a  reference  number  made  to 
correspond  with  the  numbering  on  the  azimuth  correction  device  on  the 
gun  arm  of  the  plotting  board. 

The  wind  arc  is  graduated  for  wind  components  taken  from  the  wind 
component  indicator.  The  origin  (0  wind)  is  number  50,  and  when  the 
wind  arm  is  set  on  this  number  it  is  perpendicular  to  the  deflection  scale, 
and  there  is  no  wind  correction  so  far  as  the  deflection  corrections  are 
concerned.  The  reference  number  0  corresponds  to  a  left  wind  com- 
ponent of  50  miles  per  hour,  while  the  reference  number  100  corresponds 
to  a  right  wind  component  of  50  miles  per  hour. 

The  wind  arm  is  set  to  the  proper  reference  number  by  the  arrow 
index.  The  T-square  scale  is  graduated  in  yards  of  range  plotted  really 
to  a  scale  of  times  of  flight.  The  origin  for  the  time  scale  of  the  board  is 
the  center  of  motion  of  the  travel  arm.  The  leaf-range  scale  is  used  to 
set  the  platen  for  drift;  its  principal  function  is  to  set  the  platen  for 
a  deviating  wind  component. 

To  Use  the  Board. — (1)  The  wind  arm  is  set  to  the  proper  reference 
number,  corresponding  to  the  deflection  component  as  taken  from  the 
wind-component  indicator.  (2)  The  platen  is  set  so  that  the  point  of 
the  drift  curve  corresponding  to  the  range  will  be  accurately  over  the 
right  edge  of  the  wind  arm.  (3)  The  travel  arm  (right  edge) ,  when  used, 
is  set  for  the  travel-reference  number  as  received  from  the  tally  on  the 
plotting  board.  (4)  Set  the  azimuth-correction  scale  so  that  the  travel- 
reference  number  is  under  the  normal  of  the  deflection  scale.  Then  set 
the  T  square  so  that  the  point  of  the  scale  corresponding  to  the  range  as 
called  off  from  the  plotting  board,  will  be  accurately  over  the  edge  of 
the  travel  arm.  The  beveled  edge  of  the  T  square  then  indicates  on  the 
deflection  scale,  the  deflection  to  be  used  on  the  sight  in  Cases  I  and  II, 
and  is  called  out  and  transmitted  to  the  guns  by  telephone  and  telauto- 
graph. The  beveled  edge  of  the  T  square  also  indicates  on  the  azimuth- 
correction  scale,  the  correction  to  be  applied  to  the  gun  arm  center 
of  the  plotting  board,  when  Case  III  is  used. 

When  using  Case  III,  and  when  the  time  required  to  lay  the  guns  is 
greater  than  one  observing  interval,  it  is  necessary  to  use  a  multiplying 


340  THE  SERVICE  OF  COAST  ARTILLERY 

scale,  which  can  be  attached  to  the  semicircular  brass  on  the  platen. 
These  scales  are  intended  for  use  with  either  15-  or  20-second  intervals. 
When  the  multiple  scale  is  used,  instead  of  setting  the  azimuth-correction 
scale  to  the  same  reading  as  that  of  the  travel  arm  for  travel,  it  should 
be  set  to  the  reading  of  the  multiple  scale  used,  in  which  case  the 
operations  will  then  be  the  same  as  described  above. 

For  use  during  sub-caliber  practice,  a  special  leaf  scale  and  scale  arm 
for  the  T  square  are  used,  which,  when  in  place,  permit  of  the  same 
operations  of  the  board  as  in  the  regular  drill. 


MORTAR   DEFLECTION    BOARD 

The  mortar  deflection  board  is  shown  in  Plate  XXVIII. 

It  consists  of  a  cylinder  on  which  are  numbered,  consecutively  and 
horizontally  across  the  cylinder,  azimuths  from  1  to  21  degrees,  from 
11  to  31  degrees,  etc.,  the  last  series  running  from  351  to  0  degrees  and 
then  to  11  degrees. 

The  subdivisions  of  degrees  to  five  one-hundredths  (0.05)  of  a  degree 
are  indicated  on  the  azimuth  subscale.  The  cylinder  is  revolved  by 
turning  the  azimuth  wheel  or  head  and  any  desired  series  of  azimuths' 
brought  into  the  slit  in  the  drum  shield. 

On  the  carriage  immediately  below  the  azimuth  subscale  is  the  drift 
scale  mounted  on  the  drift-scale  slide.  The  carriage  is  moved  by  turning 
the  main  traversing  wheel.  This  carriage  has  on  it  a  pointer  for  setting 
to  any  azimuth  on  the  subscale. 

The  elevation  knob  operates  a  carriage  carrying  the  two  pointers  for 
setting  the  elevation  on  the  drift  scale  and  for  indicating  the  corrected 
azimuth  on  the  subscale.  The  "  pointer  "  may  be  set  for  any  arbitrary 
correction  on  the  deflection  scale  by  turning  the  milled  head  screw. 

The  operation  of  the  board  is  as  follows: 

The  operator  (No.  4)  sets  the  small  pointer  to  the  elevation  called  out 
by  the  plotter;  he  then  brings  the  proper  degrees  on  the  cylinder  into 
the  slit  in  the  drum  shield  and  sets  the  pointer  for  the  subscale  to  azi- 
muth of  the  set-forward  point  as  called  out  by  the  assistant  plotter. 

The  corrected  azimuth  of  the  set-forward  point  is  then  indicated  by 
the  corrected  azimuth  pointer. 

The  pointer  for  the  deflection  scale  should  be  set  at  normal  or  3 
degrees  unless  it  is  desired  to  make  some  arbitrary  correction  as  the 
result  of  the  observation  of  fire. 


INSTRUMENTS,  DEVICES  AND  CHARTS 


341 


THE    WIND-COMPONENT    INDICATOR 

The  wind-component  indicator  is  an  instrument  used  to  determine, 
mechanically,  the  two  components  of  the  wind;  that  is,  the  component 
of  the  wind  which  affects  the  range,  and  that  component  which  affects 


FIG.  52. — Wind  Component  Indicator. 

the  deflection  correction.  The  component  affecting  the  range  is  used 
on  the  range  board.  That  which  affects  the  deflection  is  used  on  the 
deflection  board. 

The  instrument  is  shown  in  Fig.  52,  and  consists  of  a  dial  plate,  on 
the  face  of  which  are  reference  numbers  for  the  range  and  deflection 
components,  marked  with  their  corresponding  lines.  The  reference  num- 
bers read  from  0  on  the  left  to  100  on  the  right,  and  from  0  at  the 
bottom  to  100  at  the  top,  with  50  in  the  center.  The  dial  is  intended 


342  THE  SERVICE  OF  COAST  ARTILLERY 

to  he  held  in  a  vertical  position  by  means  of  the  arm  which  is  fastened 
to  the  back  of  the  dial  in  such  a  manner  that  the  dial  itself  will  not  turn, 
and  in  this  way  the  figures  on  it  will  always  be  right  side  up.  It  is  usually 
mounted  convenient  to  the  plotting  board,  and  where  it  can  be  seen  by 
the  range  and  deflection  computers. 

Around  the  dial  is  a  movable  azimuth  ring  graduated  and  numbered 
clockwise  for  every  5  degrees,  which  can  be  set  so  that1  the  azimuth  of 
wind  pointer,  on  the  bottom  of  the  dial,  points  to  any  required  degree. 
It  can  be  clamped  to  the  dial  in  this  position  by  'a  clamp  screw  imme- 
diately behind  the  azimuth  of  wind  pointer. 

The  target  arm  is  mounted  about  a.n  axle  so  that  it  may  be  rotated, 
and  embraces  both  the  dial  and  ring.  It  is  also  bent  in  such  a  way 
as  to  allow  it  to  pass  over  the  azimuth-ring  clamp  screw.  It  also  has  a 
clamp  screw  by  means  of  which  it  can  be  clamped  at  any  desired 
azimuth. 

The  target  pointer  passes  through  a  slot  in  the  squared  projection 
near  the  base  end  of  the  target  arm,  and  is  set  to  indicate  any  velocity  of 
the  wind  from  0  to  50  miles  per  hour,  as  shown  from  the  indicator  of  the 
aeroscope.  It  also  has  a  set  screw  by  means  of  which  it  can  be  secured 
at  any  velocity. 

To  Use  the  Board. — The  operator  (generally  the  assistant  plotter) 
first  sets  the  target  pointer  on  the  target  arm  to  the  velocity  of  the  wind, 
as  indicated  on  the  aeroscope,  or  received  over  the  telephone  from  the 
meteorological  station.  The  azimuth  ring  is  then  set  so  that  the  pointer 
at  the  bottom  of  the  dial  plate  will  show  the  azimuth  of  the  wind  as 
obtained  from  the  same  source.  The  target  arm  is  then  set  so  that  its 
(graduated)  edge  shows  the  azimuth  of  the  target  on  the  azimuth  ring, 
as  indicated  by  the  gun  arm  of  the  plotting  board,  and  it  is  necessary 
that  this  target  arm  be  moved  to  the  azimuth  of  the  target  whenever 
a  reading  is  taken.  The  position  of  the  point  of  the  target  pointer  on 
the  dial  plate  then  indicates  the  two  components  of  the  wind  which  are 
to  be  used  for  correction  purposes  on  the  range  and  deflection  boards. 
If  the  velocity  of  the  wind  or  its  direction  should  change,  the  component 
indicator  should  be  reset  and  new  components  determined. 

Taking  Fig.  52  as  an  illustration,  the  range  component  as  indicated 
is  the  reference  number  25,  while  the  deflection  component  as  indicated 
is  the  reference  number  35. 


INSTRUMENTS.  DEVICES   AND  CHARTS  .343 


AEROSCOPE 

The  aeroscope  is  a  step-by-step  dial  telegraph  used  for  sending  data 
from  the  meteorological  and  tide  stations  to  the  several  primary  stations 
of  a  battle  command. 

The  apparatus  consists  of  the  meteorological  controller,  shown  in 
Plate  XXXI,  which  is  mounted  in  the  meteorological  station,  the  tide 
controller  mounted  in  the  tide  station,  and  the  meteorological  and  tide 
indicators,  shown  in  Fig.  53,  which  are  mounted  in  the  various  primary 
stations. 

The  mechanism  of  the  indicator  consists  of  a  wheel  which  is 
rotated  in  either  direction  by  the  action  of  electromagnets  operated 
by  the  making  and  breaking  keys  of  the  controller.  The  shaft  on 
which  the  wheel  of  the  indicator  rotates  carries  a  pointer,  which,  by 
its  position  on  a  suitably  graduated  dial,  indicates  the  proper  data. 


TIME-INTERVAL    CLOCK 

The  time-interval  clock  is  shown  in  Plate  XXXII,  it  is  installed  in 
each  primary  station  of  a  battery,  fire  or  mine  command.  It  is  used  to 
operate  the  time-interval  bells  in  the  stations  and  emplacements.  The 
bells  for  any  command  ring  in  unison  at  either  15-  or  30-second  intervals. 
(Some  of  the  first  clocks  installed  ring  bells  on  15-  and  20-second 
intervals) . 

The  clock  is  spring-actuated  and  is  provided  with  an  arrangement  of 
hands  which  is  the  reverse  of  those  of  clocks  in  common  use,  the  second 
hand  being  mounted  centrally  and  sweeping  over  the  whole  face  of  the 
clock,  while  the  hour  hand  and  minute  hands  are  mounted  at  the  point 
usually  chosen  for  the  second  hand.  It  has  three  small  wheels  mounted 
on  a  shaft,  two  of  which  are  notched  so  as  to  cause  steel  pawls  to  drop 
down  and  make  three  electrical  contacts  one  second  apart,  which  give 
the  three  distinct  strokes  to  the  bell.  The  interval  depends  upon  the 
pawl  and  wheel  used.  The  pawls  are  lowered  to  the  wheels  by  means 
of  a  rod,  the  position  being  indicated  on  the  face  of  the  clock.  To 
facilitate  setting  the  bells  at  the  primary  station,  secondary  station  and 
battery  in  step,  a  starting  and  stopping  button  is  provided;  this  button 
is  connected  to  a  light  spring  which  acts  on  the  escapement  wheel, 
stopping  and  starting  the  same. 


344 


THE  SERVICE  OF  COAST  ARTILLERY 


Wind  Azimuth  Dial 
giving  Azimuth  of 


Wind  Velocity  Dia 

giving  Velocity  of 

Wind  in  Miles 

per  Hour 


Atmosphere  Density 
Dial  giving  percent- 
age Density  of  the 

Atmosphere  in 
Reference  Numbers 


Tide  Dial 
giving  Stat»  of 
Tide  in  Feet 
and  Hundredths 


FIG.  53. — Aeroscope  Indicator. 


INSTRUMENTS,  DEVICES  AND  CHARTS  345 


THE    INTERRUPTER 

The  interrupter  is  shown  in  Plate  XXXII.  It  is  a  form  of  buzzer 
arranged  to  provide  comparatively  'slow  interruptions  of  the  time- 
interval  bell  circuit.  The  coil  of  the  interrupter  is  in  shunt  across  the 
signal  circuit  and  its  armature  is  provided  with  an  auxiliary  break, 
which  causes  the  armature  of  the  single  stroke  bells  to  vibrate  in  unison 
with  it. 

Interrupters  are  mounted  on  brackets  in  the  primary  base-end  stations. 


THE    TELAUTOGRAPH 

The  telautograph  is  shown  in  Plate  XXXII.  It  is  an  electro- 
mechanical instrument  which  transmits  and  simultaneously  reproduces 
handwriting  or  sketches  at  a  distance. 

In  the  coast  artillery  service  these  instruments  are  used  to  transmit 
data  from  the  plotting  rooms  of  the  primary  stations  to  the  gun  emplace- 
ments and  mortar  emplacements. 

The  telautograph  equipment  for  a  battery  consists  of  a  transmitter 
mounted  in  the  plotting  room,  a  receiver  mounted  within  view  of  a 
transmitter,  as  a  "  pilot  "  or  guide  receiver,  and  several  receivers,  usually 
two,  mounted  in  moisture-proof  cases  and  installed  on  the  gun  carriages 
at  the  battery  or  in  an  emplacement  booth.  The  instruments  are  con- 
nected to  the  line  wires  in  series,  the  line  currents  passing  through  all  the 
receivers  in  turn,  and  all  receivers  write  the  same  message  simultaneously. 
Three  line  wires  are  used,  one  called  the  "  right  line,"  which  operates 
the  mechanism  of  the  right  side,  and  one  called  the  "  left  line/'  which 
operates  the  mechanism  of  the  left  side.  The  third  wire  carries  the 
current  which  actuates  the  pen-lifters  and  relays;  this  is  called  the 
"  pen-lifter  line." 

The  instruments  require  110  volts  direct  current  and  each  uses  about 
one  ampere  during  actual  operation.  This  power  is  obtained  from  a 
storage  battery  over  separate  power  leads  and  is  independent  of  the 
emplacement  lights  or  motors. 

Messages  written  on  the  transmitter  are  reproduced  upon  the  pilot 
receiver  and  similarly  on  all  the  outlying  receivers,  the  pens  moving  in 
unison  with  the  transmitter  pencil.  The  method  of  switching  the  power 
on  and  off  at  the  transmitter  operates  the  paper  shifting  magnet  in  all 
the  receivers. 


346  THE  SERVICE  OF  COAST  ARTILLERY 


THE   TELEPHONE 

In  addition  to  using  the  telephone  properly  it  is  important  that  the 
operator  should  have  sufficient  knowledge  of  the  theory  and  general 
construction  of  the  types  of  telephones  used  in  the  seacoast  service  to 
correct  minor  defects  or  at  least  determine  where  the  troubles  lie  in 
order  to  make  intelligent  report  to  those  charged  with  their  repair. 

Anyone  can  use  a  telephone,  with  but  little  practice,  but  to  do  so 
accurately  and  with  such  certainty  .necessary  in  coast  artillery  work 
requires  careful  instruction  and  constant  training. 

The  standard  telephone  system  now  used  in  fire-control  work  is  tech- 
nically known  as  the  composite,  common  and  local  battery  system. »  The 
several  types  of  instruments  are  shown  in  Plate  XXXII  and  the  dia- 
gram of  their  circuits  is  shown  in  Fig.  54. 

The  theory  of  the  telephone  may  be  briefly  stated  as  follows: 

The  act  of  speaking  produces  sound  waves  of  varying  intensity  which 
fall  upon  the  drum  of  the  ear  and  are  recognized  by  the  auditory  nerves 
as  speech.  If  these  sound  waves  instead  of  falling  upon  the  ear  drum, 
strike  against  a  thin  diaphragm  such  as  that  found  in  the  transmitters 
of  the  ordinary  telephones,  these  vibrations  become  electrical  and  are 
capable  of  being  reproduced  at  the  other  end  of  the  line,  that  is,  in  the 
receiver  of  the  distant  telephone. 

Referring  to  the  diagram,  Fig.  54,  when  the  receiver  r  is  removed 
from  the  hook  h  current  comes  to  the  line  through  the  retardation  coil  C, 
over  the  line  a,  through  the  induction  coil  S,  through  contact  of  the  hook 
switch  v,  through  the  connection  n,  through  the  transmitter  t,  through 
the  connection  e  and  back  over  d  through  the  retardation  coil  and  to 
the  other  pole  of  the  battery. 

Changes  in  resistance  of  the  transmitter  due  to  the  sound  waves  of 
the  voice  striking  the  diaphragm  cause  corresponding  changes  in  the 
current  on  the  line,  and  a  change  of  potential  (pressure)  at  the  terminals 
of  the  retardation  coil  inductively  affects  the  coil  T  of  the  induction  coil, 
this  induced  current  passes  through  the  receiver  r  and  the  operator  hears 
himself  speak;  the  current  also  goes  through  the  transmitter,  the  con- 
denser and  back  to  coil  T.  The  same  effect  as  that  produced  in  the 
home  receiver  is  produced  in  all  receivers  on  the  line,  the  current  in  the 
distant  induction  coil  being  altered  by  change  of  potential  at  the 
retardation  coil. 

The  condenser  k  is  introduced  into  the  circuit  to  strengthen  the  trans- 
mission and  produce  clearness  of  speech.  Changes  in  the  transmitter 


INSTRUMENTS,  DEVICES  AND  CHARTS 


347 


resistance  produce  corresponding  changes  in  potential  between  the  trans- 
mitter terminals,  through  I  to  e  on  one  side  of  the  condenser  and  through 
the  receiver  and  coil  T  to /on  the  other  %side.  The  condenser  will  there- 


JOOOOhn 


induction  Coil  \ 


TO  Ohms 


'ye  f /  on  Coil 


fnductionCoil  \ 


"FT 


4O  Ohms\3jg  Retardation  Coif 

C 
4OOhms-\ 


30  Volts 
Common  Battery 


Induction  Coil 


FIG.  54. 


fore  be  charged  and  discharged  through  the  coil  T,  producing  current 
ripples  which  will  inductively  affect  the  coil  Tt  and  tend  to  amplify 
corresponding  changes  of  current  in  T. 


348  THE  SERVICE  OF  COAST  ARTILLERY 

In  case  of  failure  of  the  common  battery  the  switches  at  8  and  S'  are 
closed,  putting  the  local  battery  circuit  through  the  primary  coil  P, 
which  then  acts  inductively  on  S  as  a  secondary  and  tjie  induced  current 
passes  to  the  line  through  the  distant  coil  $',  and  acts  inductively  on 
the  coil  T  and  the  receiver  circuit. 

The  magneto  m  and  the  ringer  g  are  in  parallel  on  one  side  of  the  line 
a,  with  the  condenser  k  between  them  and  the  other  line  d.  The  magneto 
is  connected  to  the  line  through  the  condenser  because  the  heavy  gener- 
ator windings  of  comparatively  low  resistance  would  otherwise  tend  to 
cause  the  armature  to  "  stick  "  when  the  crank  is  turned.  This  "  stick- 
ing "  is  due  to  the  direct  current  on  the  line  which  would  pass  through 
the  armature  of  the  magneto. 

* 
OPERATION 

Selection  of  Operators. — The  operator  should  be  of  a  non-excitable 
disposition,  so  as  to  speak  slowly  and  distinctly  at  all  times.  He  should 
articulate  well  and  never  speak  too  loud.  No  person  should  be  selected 
as  operator  until  he  has  been  tried  on  a  line  that  is  not  working  very 
well,  for  a  test  of  the  suitability  of  his  voice  for  the  work.  Too  much 
stress  cannot  be  laid  on  the  necessity  for  care  in  the  selection  of  tele- 
phone operators. 

If  each  operator  takes  an  interest  in  the  instrument  he  uses  and  applies 
proper  care,  the  efficiency  of  the  system  will  be  increased  twofold.  The 
talking  sets  should  be  hung  in  their  proper  places  at  the  completion  of 
drill;  hook  retaining  springs  attached;  cords  kept  clear  of  possible 
interference;  and  a  prompt  report  made  of  any  defect  found. 

To  Open  Station. — Care  must  be  taken  in  this  ordinary  operation  in 
order  to  detect  any  evident  trouble  before  the  work  begins  and  thus 
avoid  interruption.  The  following  simple  rules  should  be  observed: 

(a)  Look  over  the  connections  to  see  if  none  is  loose.  These  are  the 
two  connections  to  line  and  the  three  where  the  head  set  is  attached  at 
terminal  block,  the  battery  terminals,  if  local  battery  is  used. 

(6)  Release  the  retaining  spring  and  see  that  the  hook  goes  all  the  way  up 
or  till  good  contacts  are  made  at  v. 

(c)  Put  the  head  set  on  and  close  the  two-way  switches  to  C  B  and 
then  to  L  B.  In  both  cases  a  distinct  click  should  be  heard.  Leaving 
the  switch  on  the  common  battery,  lower  and  raise  the  hook  switch  when 
the  same  click  should  be  heard.  Experience  will  teach  the  operator  how 
loud  this  click  should  be.  A  slight  scratching  in  the  transmitter  should 
be  heard  in  the  receiver. 


INSTRUMENTS,  DEVICES  AND  CHARTS  349 

(d)  Hold  hook  down  and  ring  the  station  and  wait  for  a  reply  (unless 
the  phones  are  connected  through  a  central),  in  which  case  no  ringing 
is  necessary. 

(e)  Place  the  mouth  near  the  mouthpiece  of  the  transmitter  and  call 
the  other  station  by  name.     Wait  for  a  verbal  answer  to  the  call  before 
sending  any  message.     A  little  delay  at  this  stage  may  result  in  a 
material  gain  of  time. 

Using  the  Phone. — Although  a  simple  operation,  too  much  care 
cannot  be  taken  to  do  this  properly. 

(a)  Never  shout,  as  this  causes  a  rattling  of  the  diaphragm  with  a 
consequent  jumbling  of  the  sounds. 

(6)  Place  the  mouth  at  a  distance  of  from  one  to  two  inches  from  the  trans- 
mitter and  speak  slowly  and  distinctly,  not  slurring  over  words  or  syllables, 
but  enunciating  clearly  each  sound.  The  distance  of  the  mouth  from 
the  receiver  is  determined  by  practice  and  depends  on  the  character  and 
carrying  power  of  the  voice. 

It  is  not  desirable  that  the  air  expelled  from  the  mouth  in  the  act  of 
speaking  strike  the  diaphragm,  as  this  may  set  up  vibrations  different 
from  those  due  to  the  sound  wave  and  cause  confusion. 

To  prevent  this  the  voice  should  be  directed  to  one  side  of  the  trans- 
mitter, or  the  mouth  may  be  placed  at  the  side  of  and  touching  the 
transmitter  opening  and  the  voice  directed  across  it. 

(c)  Unless  absolutely  necessary,  do  not  use  any  unusual  words,  ad- 
hering to  those  heard  every  day  about  the  guns. 

(d)  Endeavor  to  complete  every  sentence  without  break  or  change. 
For  this  reason  every  important  message  should  be  written  and  the 
operator  should  read  it  before  beginning  to  transmit  it. 

(e)  Send  numerals  singly,  thus  4370  is  sent  four,  three,  seven,  zero. 
The  use  of  the  letter  O  for  a  zero  may  sound  like  the  numeral  four. 
Mistakes  due  to  this  are  known  to  have  occurred. 

Enunciate  clearly  and  speak  slowly,  as  each  word  stands  by  itself;  the 
adjacent  words  do  not,  as  in  a  message,  help  to  determine  one  not  under- 
stood. If  it  is  necessary  to  repeat,  use  more  care  as  to  distinctness  and 
do  not  yell. 

If  necessary,  a  numeral  not  understood  may  be  accentuated  by  count- 
ing up  to  it  and  emphasizing  it.  Thus  if  the  4  is  not  understood  in 
7649  begin  to  count  one,  two,  three,  FOUR. 

(/)  In  receiving,  close  attention  is  necessary;  the  senders  hould  be 
interrupted  only  when  absolutely  necessary  and  the  part  to  be  repeated 
clearly  indicated. 

If  the  sender  begins  to  speak  too  loud,  the  receiver  must  caution  him 


3.50  THE  SERVICE  OF  COAST  ARTILLERY 

to  speak  lower  and  continue  to  do  so  until  the  best  pitch  of  voice  is 
obtained. 

All  unnecessary  conversation  must  be  absolutely  prohibited  if  satis- 
factory results  are  desired. 

To  Close  Station. — Repeat  to  the  other  stations  what  has  been 
ordered,  then  hang  up  the  head  set  on  the  hook  and  open  the  switch  in 
the  local  circuit  if  it  has  been  used.  If  the  head  set  is  not  to  be  hung 
on  the  hook  see  that  the  retaining  spring  is  made  fast  to  insure  the 
breaking  of  the  contact  at  v,  Fig.  54. 


TESTING 

Remarks. — Experience  is  the  best  guide  in  quickly  locating  and  cor- 
recting faults  in  the  telephone,  but  a  familiarity  with  the  parts  of  the 
phone  and  what  each  is  supposed  to  do,  together  with  a  few  rules  of 
procedure,  coupled  with  a  primary  knowledge  of  electrical  principles, 
will  enable  a  novice  to  locate  trouble  even  though  he  cannot  cure  it. 

General  Principles. — It  is  evident  that  the  field  ctf  the  trouble  can 
always  be  narrowed  down  considerably  by  disconnecting  the  phone  from 
the  line.  If,  on  so  doing,  the  trouble  disappears  it  must  have  been  in 
the  line.  In  any  case  of  trouble  look  carefully,  but  rapidly  over  the 
whole  phone,  as  the  cause  is  sometimes  quite  evident  to  the  eye,  partic- 
ularly if  it  is  a  disconnected  wire  or  a  loose  joint.  Failing  to  see 
the  trouble,  proceed  with  the  operator's  test. 

The  troubles  generally  lie  under  five  heads,  as  given  below.  Each 
case  is  analyzed  and  the  possible  sources  of  troubles  enumerated,  with 
the  tests  for  determining  which  exists.  The  term  indicated  is  used  ad- 
visedly in  the  tests  because  in  obscure  troubles  the  symptoms  may 
be  deceptive. 

A.       BELL   IS    NOT    RUNG    BY   ITS    OWN    MAGNETO 

Analysis — 

1.  Short  circuit  on  line,  or 

2.  Mechanical  trouble  in  the  bell,  or 

3.  Short  circuit  in  the  phone,  or 

4.  Open  circuit  in  the  phone,  or 

5.  Magneto  does  not  generate. 

Operator's  Test. — With  the  receiver  on  the  hook  turn  the  magneto 
handle  briskly  twTo  or  three  times.  If  the  bell  does  not  ring  and  the 


INSTRUMENTS,  DEVICES  AND  CHARTS  351 

magneto  turns  hard,  i.  e.,  with  more  difficulty  than  when  the  phone  is 
in  good  order  1.  (Short,  circuit  on  line),  or,  3.  (Short  circuit  in  phone)  is 
indicated  and  the  operator  proceeds  as  follows,  trying  to  ring  after 
each  step: 

*  Inspect  and  see  that  the  ends  of  the  line  and  xground  wires  do  not 
touch  any  other  part  after  passing  through  the  binding  posts. 

Disconnect  the  line  wires,  if  the  bell  rings  now,  1  (Short  circuit  on  line) 
is  clearly  indicated  and  should  be  reported,  but  if  it  does  not  ring  and 
still  turns  hard,  report  that  3  (Short  circuit  in  phone)  is  indicated. 

If  the  handle  does  not  turn  hard  the  operator  takes  up  2  (Mechanical 
trouble  in  the  bell)  and  sees  that  the  striker  is  not  bound  by  the  metallic 
cap  over  it,  also  that  the  armature  can  be  moved  by  hand  and  that  the 
striker  will  touch  the  gongs  when  the  armature  is  so  moved.  The  first 
trouble  may  be  remedied,  the  others  should  be  reported. 

Proceed  next  to  4  (Open  circuit  in  the  phone)  and,  opening  the  mag- 
neto box,  see  if  contact  is  made  between  shaft  and  spring  when  th/* 
handle  is  turned.  The  last  may  fail  because  the  shaft  is  caught  at  some 
place,  as  where  it  enters  the  box,  or  the  collar  on  the  shaft  may  have 
slipped  or  the  springs  may  be  bent.  The  spring  may  be  held  against 
the  end  of  the  shaft  with  a  pencil,  during  a  test,  to  insure  good  contact. 
A  spark  seen  at  this  contact  indicates  poor  contact.  If  the  operator 
cannot  easily  correct  these  faults  he  should  report  as  nearly  as  practicable 
what  trouble  he  has  found. 


B.       BELL    IS    NOT   RUNG    BY    DISTANT    MAGNETO 

Analysis— 

1.  Home  phone  out  of  order,  or 

2.  Distant  phone  out  of  order,  or, 

3.  Line  out  of  order. 

4.  Condenser  circuit  open. 

Operator's  and  Expert's  Test 

(a)  Test  for  1  (Home  phone  out  of  order)  by  detaching  the  line  and 
turning  the  handle,  and  proceed  as  under  A. 

(b)  Test  for  2  (Distant  phone  out  of  order)  at  the  distant  phone  in  a 
manner  entirely  similar  to  1   (Home  phone  out  of  order) . 


352  THE  SERVICE  OF  COAST  ARTILLERY 

C.   CAN  HEAR  BUT  CANNOT  BE  HEARD 

Analysis— 

1.  Local  circuit  at  fault. 

(a)   Battery,  (6)   connections  or  wiring,  (c)  transmitter, 
(d)  primary  coil,  or 

2.  Distant  receiver  out  of  order,  or 

3.  Home  secondary  coil  short-circuited. 

Operator's  Test. — Disconnect  line  wires  and  connect  binding  posts 
with  a  piece  of  wire,  thus  short-circuiting  the  phone.  Place  the  receiver 
to  the  ear  and  scratch  gently  with  the  finger  nail  on  the  inside  of  the 
transmitter  mouthpiece.  If  this  is  distinctly  -heard  the  local  circuit 
and  receiver  are  all  right. 

If  no  sound  results  put  the  receiver  to  the  ear,  lower  and  raise  hook, 
also  open  and  close  the  two-way  switch.  If  a  distant  click  is  heard  for 
each  of  these,  the  local  circuit  is  all  right ,  but  the  transmitter  may  not  be 
in  good  order,  and  a  report  should  be  so  made. 

If  no  sound  results,  make  sure  that  the  switch  contact  is  good,  on 
CB  and  LB,  that  the  pivot  is  not  loose,  that  contacts  at  v  are  good, 
that  the  connections  at  battery  terminals  are  good. 

(Distant  receiver  out  of  order).  The  operator  at  the  distant  phone 
should  try  the  tests  above  given  for  home  circuit.  If  these  give  no 
sound  in  his  receiver  he  should  try  another  receiver,  if  one  is  available. 
He  may  try  a  new  cord  or  substitute  pieces  of  wire  for  it. 

D.  CAN  NEITHER  HEAR  NOR  BE  HEARD 

Analysis — This  indicates  general  trouble. — 

1.  In  the  phones,  or 

2.  In  the  line. 

Operator's  Test. — Go  over  the  phone  carefully,  looking  for  poor  con- 
tacts as  where  an  insulated  wire  is  put  in  the  binding  posts ;  binding  posts 
not  screwed  down  tight;  ends  of  wires  passing  through  post  and  touching 
other  parts;  contacts  at  cells  and  condition  of  cells  as  noted  before. 
Disconnect  the  line  wires  and  test  out  phones  as  indicated.  If  there  are 
fuses  in  the  line  see  that  they  are  not  burned  out.  If  no  trouble  is 
found  to  exist  when  the  line  is  disconnected  report  line  out  of  order. 


INSTRUMENTS,  DEVICES  AND  CHARTS  353 


MERCURIAL   THERMOMETER 

The  temperature  of  the  air  is  measured  by  means  of  a  mercurial  ther- 
mometer. This  instrument  consists  of  a  glass  tube  having  a  very  small 
bore,  terminating  in  a  bulb,  and  containing  mercury. 

It  is  founded  on  the  principle  that  changes  of  temperature  in  bodies 
are  accompanied  by  proportional  changes  in  their  volumes  or  dimen- 
sions. When  the  temperature  rises,  the  mercury  in  the  bulb  expands 
more  than  the  glass  and  rises  in  the  tube;  when  the  temperature  de- 
creases the  mercury  contracting  more  than  the  glass  descends  again 
towards  the  bulb.  The  changes  in  temperature,  to  which  the  thermo- 
meter is  exposed,  will  therefore  be  shown  by  the  rising  and  falling  of 
the  mercury  in  the  tube. 

In  order  to  have  an  intelligent  measure  of  these  changes  the  ther- 
mometer is  provided  with  a  fixed  scale.  The  two  fixed  temperatures — • 
one  of  melting  ice,  usually  called  the  freezing  point;  and  the  other  that 
of  boiling  water  under  standard  pressure,  or  rather  the  temperature  of 
the  steam  above  the  surface  of  boiling  water — have  been  adopted  as  the 
fixed  or  starting  points'  for  the  graduations  of  thermometers.  The 
intervals  between  these  two  fixed  points  are  divided  into  spaces  called 
degrees,  and  for  coast  artillery  work  these  are  divided  into  sub-spaces, 
called  hundredths  of  degrees. 

The  Fahrenheit  thermometer  is  marked  32  degrees  at  the  point  of 
melting  ice  and  212  degrees  at  the  point  of  boiling  water,  the  space  be- 
tween these  two  graduations  being  divided  into  180  equal  parts.  The 
graduations  being  divided  into  180  equal  parts.  The  graduations  ex- 
tend downward  to  zero,  and  usually  10  or  20  degrees  below  zero. 

The  Fahrenheit  scale  is  generally  used  in  connection  with  coast 
artillery  work,  but  readings  made  on  the  centigrade  thermometer  are 
readily  converted.  The  freezing  point  on  the  centigrade  is  marked 
zero  and  the  boiling  point  100.  It  is  therefore  necessary,  in  order  to 
convert  Fahrenheit  readings  to  centigrade,  to  subtract  32  degrees  and 
multiply  the  remainder  by  f ;  or,  to  convert  centigrade  to  Fahrenheit 
readings,  multiply  by  f  and  add  32  degrees.  Mercurial  thermometers 
can  be  relied  upon  down  to  temperatures  near  the  point  of  freezing 
mercury,  or  as  low  as  minus  38  degrees. 


354  THE  SERVICE  OF  COAST  ARTILLERY 


THE   BAROMETER 

The  density  of  the  air  is  measured  by  means  of  the  barometer  and 
thermometer.  The  barometer  depends  for  its  action  upon  the  principle 
that  air  has  weight.  As  is  generally  known,  the  weight  of  air  w;ll  uphold 
a  column  of  water  the  vertical  height  of  which  depends  upon  the  height 
above  the  sea  level  at  which  the  experiment  is  conducted. 

In  the  coast  artillery  service  the  jnercurial  barometer  is  used  prin- 
cipally to  test  the  adjustment  of  the  aneroid  barometer.  The  latter, 
being  quicker  in  its  action,  is  used  in  connection  with  the  thermometer  to 
determine  the  reference  number  on  the  atmosphere  board,  to  be  applied 
on  the  atmosphere  density  per  cent,  indicator  of  the  aeroscope. 

Mercurial  Barometer. — This  barometer  consists  of  a  glass  tube  about 
a  yard  in  length  closed  at  the  top  and  open  at  the  bottom,  which  is 
partially  filled  with  mercury.  The  tube  is  suspended  vertically,  as  shown 
in  Plate  XXXI.  The  lower  end  of  the  tube  dips  into  a  cistern,  which 
consists  of  a  brass  casing,  including  three  wooden  pieces  fastened  to- 
gether by  four  screws  in  the  form  of  a  circle.  The  lower  portion  of  the 
cistern  has  a  leather  sack,  called  the  cistern  sack,  which  can  be  raised  or 
lowered  by  means  of  an  adjusting  screw.  It  is  used  to  bring  the  surface 
of  mercury  in  the  cistern  to  a  certain  level  before  a  reading  is  taken. 

In  preparing  the  instrument  for  use  the  top  is  first  completely  filled 
with  mercury.  As  soon  as  it  is  free  to  do  so  the  column  of  mercury  in  the 
tube  sinks  until  it  stands  at  a  height  of  about  30  inches,  or  such  that  the 
pressure  of  the  column  exactly  balances  that  of  the  atmosphere.  A 
graduated  scale  of  metal  is  attached  to  the  glass  and  affords  the  means 
of  reading  the  height  of  the  column  of  mercury. 

To  read  the  barometer  first  read  the  attached  thermometer  to  the 
nearest  half  degree  'and  record  it.  Tap  the  barometer  sharply  with 
the  finger  to  free  the  mercury  from  the  tube.  By  means  of  the  adjusting 
screw  lower  the  mercury  in  the  cistern  below  and  then  raise  it  until  the 
surface  exactly  touches  the  ivory  point.  When  the  mercury  is  per- 
fectly clean  the  proper  adjustment  can  be  made  by  causing  the  ivory 
point  to  exactly  coincide  with  its  reflected  image  in  the  mercury  below. 
But  usually  after  the  mercury  has  been  in  use  for  a  short  time  a  slight 
film  of  oxide  forms  on  its  upper  surface  and  it  is  necessary  to  determine 
the  contact  by  immersing  the  ivory  point  in  the  mercury  until  a  slight 
dimple  is  formed,  and  then  slightly  lower  the  screw  until  the  dimple  is 
about  to  disappear. 

Adjust  the  vernier  by  means  of  the  side  mill-headed  screw  to  the  top 


PLATE   XXXI 


SERVICE 
AEROSCOPE   | 
ONTROLLER- 


ANERCMD 
AROMETE 


Azimuth  of 

in  degrees 
terrruned  from 
wind  vane 


•ind  miles 
per  hour 


letermtned  from 

memometer  and 


Density  of 
atmosphere 

per  cent, 
determined  from 
itmosphere  board 


m 

SI  STANDARD 
I1  MERCURIAL 
i'  8AROMETEF 


Equipment  of  Meteorological  Station. 


OF   THE 

UNIVERSITY 

OF 


INSTRUMENTS,  DEVICES  AND  CHARTS 


355 


of  column  of  mercury  until  the  zero  line  of  the  vernier  and  the  bottom 
of  the  hind  part  of  the  vernier  in  rear  of  the  mercurial  column  exactly 
coincides  with  the  top  of  the  meniscus,  that  is,  tangent  to  the  convex 
surface  of  the  mercury  in  the  tube.  Read  the  barometer  scale  to  inches 
and  tenths  between  the  zero  point  and  the  lowest  line  of  the  vernier. 
Find  the  number  of  the  line  on  the  vernier  which  coincides  most  nearly 
with  the  line  on  the  barometer  scale.  (See  Fig.  55.)  This  number  will 
be  the  hundredths  of  an  inch  of  the  barometer  reading.  Add  to  this 
the  inches  and  tenths  and  the  result  will  be  the  barometer  reading  in 


80.011. 


20.999. 

FIG.  55. 


28.820. 


inches,  tenths  and  hundredths.  Where  a  line  on  the  vernier  does  not 
exactly  coincide  with  the  line  on  the  barometer  scale  the  observer  will 
after  practice  be  able  to  estimate  the  reading  to  thousandths  of  an  inch. 
Be  careful  in  making  the  adjustments  of  a  barometer  suspended  from 
one  end  only  so  as  not  to  move  the  barometer  from  its  vertical 
position. 

Aneroid  Barometer. — The  aneroid  barometer,  shown  in  Plate  XXXI, 
consists  of  a  cylindrical  metal  box  exhausted  of  air,  having  a  lid  of  thin 
corrugated  metal.  The  lid,  which  is  highly  elastic,  yields  to  every 
change  of  atmospheric  pressure  and  delicate  springs  and  levers  transmit 


356  THE  SERVICE  OF  COAST  ARTILLERY 

its  motions  to  an  index  that  moves  over  a  graduated  scale  whose  divi- 
sions are  marked  on  the  dial  after  comparison  with  the  mercurial 
barometer. 

All  aneroids  should  be  frequently  and  carefully  tested  with  standard 
mercurial  instruments  at  known  altitudes  in  order  to  determine  the 
proper  correction  for  instrumental  error.  The  best  aneroids  are  now 
marked  compensated  and  are  practically  free  from  errors  arising  from 
changes  of  temperature  in  the  instrument  itself. 

One  of  the  chief  differences  between  the  aneroid  and  the  mercurial 
barometer  is  the  fact  that  the  aneroid  acts  more  rapidly  under  rapid 
changes  of  pressure  than  does  the  mercurial  barometer,  and  care  should 
be  taken  to  avoid  errors  due  to  the  sluggishness  of  the  mercurial  bar- 
ometer. 

Aneroids  are  usually  graduated  to  indicate  a  fall  of  pressure  to 
twenty  inches,  which  would  correspond  to  a  height  of  a  little  over 
11,000  feet. 


THE    ANEMOMETER 

The  velocity  of  the  wind  is  determined  by  an  instrument  called  the 
anemometer.  The  type  in  use  at  seacoast  fortifications  is  known  as  the 
Robinson  type,  and  consists  of  a  vertical  spindle  having  at  its  upper  end 
four  horizontal  arms  at  right  angles  to  one  another,  bearing  at  their  ex- 
tremities hollow  hemispherical  aluminum  cups  whose  circular  rims  are 
in  the  vertical  plane  passing  through  the  respective  arms  and  the  com- 
mon axis  of  rotation.  The  convex  side  of  each  cup  faces  the  direction 
of  rotation.  Therefore  two  opposite  cups  have  their  convex  surfaces 
facing  in  opposite  directions.  The  pressure  of  the  wind  against  the  cup 
whose  concave  side  receives  the  wind  is  greater  than  against  the  cup 
whose  convex  side  receives  it  at  the  same  time.  Consequently,  whatever 
the  direction  of  the  wind,  the  cups  are  caused  to  rotate  in  the  same  direc- 
tion, each  cup  moving  with  its  convex  side  forward. 

On  the  lower  portion  of  the  vertical  spindle  there  is  a  worm  gearing 
into  a  worm  wheel,  and  on  the  arbor  of  this  wheel  another  worm  gears 
into  a  pinion  and  the  pinion  in  turn  gears  into  the  teeth  on  the  circum- 
ferences of  the  dials  driven  by  them.  The  mechanism  is  arranged  to 
close  an  electric  circuit  at  the  expiration  of  a  certain  number  of  revolu- 
tions of  the  cups.  In  the  type  in  use  the  contact  is  so  arranged  that  it  is 
closed  once  every  25  revolutions  of  the  spindle,  which  corresponds  to 
•^  of  a  mile  travel  of  wind,  with  certain  corrections -as  the  velocity  rises. 


INSTRUMENTS,  DEVICES  AND  CHARTS  • 


357 


The  connections  and  general  arrangement  of  the  anemometer  are  shown 
in  Fig.  56. 

The  rapidity  with  which  the  air  moves  past  any  given  point  of  the 
earth's  surface  is  called  the  velocity  of  the  air  or  wind  at  that  point. 
On  account  of  the  friction  of  the  moving  air  in  contact  with  the  surface 
of  the  earth  the  movement  of  the  air  is  retarded  near  the  surface.  It  is 
estimated  that  the  effect  of  this  friction  decreases  from  20  to  50  per  cent, 
for  the  first  100  feet  above  the  earth,  and  gradually  diminishes  until  its 
effect  is  nil  at  an  elevation  of  10,000  feet.  For  this  reason  anemometers 
are  installed  at  the  highest  available  point  in  fortifications. 


Anemometer 


Battery 


FIG.  56. 

Method  of  Using  the  Instrument. — As  previously  stated,  the  approxi- 
mate velocity  of  the  wind  in  miles  per  hour  is  equal  to  180  divided  by  the 
time  between  the  closing  of  the  contacts  of  the  anemometer.  An  ane- 
mometer stop  watch  reading  to  £  second  and  marked  on  its  face  in  red 
figures  at  the  points  corresponding  to  40,  30,  20,  10  and  5  miles  per  hour 
is  used  in  connection  with  the  anemometer  in  determining  the  velocity 
of  the  wind.  At  the  first  closing  of  the  contact  which  clicks  a  sounder 
or  rings  a  bell  the  stop  watch  is  started,  and  at  the  next  closing  of  the 
circuit  which  gives  the  same  signal  the  watch  is  stopped.  The  velocity 
of  the  wind  in  miles  per  hour  is  indicated  as  above  stated  in  red  figures 
upon  the  dial  of  the  watch,  or  in  case  the  anemometer  stop  watch  is  not 
at  hand  the  velocity  may  be  obtained  from  the  following  table: 


358 


THE  SERVICE  OF  COAST  ARTILLERY 


Seconds 
Interval 
Between 
Strokes 
of  Bell  or 
Sounder. 

Velocity  of 
Wind,  Miles 
per  Hour. 

Seconds 
Interval 
Between 
Strokes 
of  Bell  or 
Sounder. 

Velocity  of 
Wind,  Miles 
per  Hour. 

2J 

53 

12 

14 

3 

45 

14      , 

12 

3£                      40 

16 

11 

4~ 

36 

18 

9.5 

5 

30 

20 

8 

6 

26 

25 

6.5 

7 

23 

30 

5.5 

8 

20 

-35 

5 

9 

18 

40 

4.5 

10 

16 

60 

3.0 

THE    ATMOSPHERE    BOARD 

The  atmosphere  board  is  used  to  determine  the  atmosphere  reference 
numbers  to  be  recorded  on  the  density  dial  of  the  aeroscope  indicator. 
It  is  shown  in  Fig.  57. 

ATMOSPHERE  BOARD 


FIG.  57. 


The  board  consists  of  a  frame  upon  which  a  graphic  table  is  mounted. 
Along  the  top  edge  of  the  frame  a  T-square  fits  into  a  groove  which  runs 
the  length  of  the  board.  The  arguments  of  the  table  are  barometer  and 


PLATE  XXXII 


Instrument  Panel,  Fire-Control  Equipment  for  Primary  Station. 


OF   THE 

UNIVERSITY 

OF 


INSTRUMENTS,  DEVICES  AND  CHARTS  359 

thermometer  readings.  The  thermometer  graduations  are  horizontal 
and  extend  along  the  top  of  the  table  while  the  barometer  graduations 
are  vertical  and  extend  along  the  right  side  of  the  table,  and  for  con- 
venience of  reading,  are  also  placed  along  the  left  edge  of  the  T-square. 
The  reference  numbers  are  indicated  on  diagonal  lines  as  shown  in 
Fig.  57. 

To  Use  the  Chart. — Assuming  that  the  thermometer  shows  a  tempera- 
ture of  20.10  degrees  and  the  barometer  a  pressure  of  29.50  inches,  the 
ruler  of  the  T-square  is  moved  until  its  left  edge  is  made  to  coincide 
wdth  the  reading  of  20.10  degrees.  The  atmosphere  reference  number 
will  then  be  the  nearest  diagonal  line  cutting  the  barometer  graduations 
on  the  ruler  at  29.50.  An  inspection  of  Fig.  57  will  show  this  diagonal 
line  to  be  numbered  8.  Therefore  the  reference  number  for  the  ther- 
mometer and  barometer  readings  taken  would  be  8.  This  number 
would  then  be  indicated  on  the  density  dial  of  the  aeroscope. 


SIGHTS 

Sights  for  scacoast  cannon  are  of  two  general  classes,  namely:  Open 
Sights,  and  Telescopic  Sights. 

OPEN  SIGHTS. 

2.24-inch  6-pounder,  Wheeled  Mount. — Open  tangent  (front  and 
rear)  sights,  affixed  to  the  gun  in  the  ordinary  manner,  are  issued  with 
these  guns. 

The  front  sight  consists  of  a  bracket  and  a  cross-wire  frame;  the 
latter  carries  two  wires  and  is  assembled  in  the  socket  of  the  former  by 
a  stud  and  set  screw. 

The  rear  sight  consists  of  a  bracket,  an  operating  knob,  a  pinion  with 
a  sleeve,  a  standard,  a  cross  arm  and  screw,  and  a  cross-wire  frame. 
The  bracket  is  slotted  for  the  standard  and,  at  right  angles,  for  the 
pinion  and  sleeve.  The  sleeve  and  the  knob  are  assembled  to  the 
pinion  and  are  held  in  place  by  the  pinion  wheel  and  a  spring  that 
abuts  against  a  shoulder  on  the  knob  and  a  collar  fastened  at  the  outer 
end  of  the  pinion. 

The  sleeve  is  assembled  to  the  bracket  by  a  set  screw,  and  has  a  ser- 
rated surface  that  fits  a  corresponding  surface  on  the  knob,  thus  pre- 
venting rotation  of  the  latter.  The  knob  is  ordinarily  held  against  the 
sleeve  by  the  spring,  but  may  be  moved  along  the  pinion  and  then 


360  THE  SERVICE  OF  COAST  ARTILLERY 

rotated,  a  spline  on  the  pinion  and  a  corresponding  groove  in  the  knob 
causing  them  to  rotate  together. 

The  standard  is  shaped  to  the  slot  in  the  bracket,  has  the  ranges 
marked  on  its  surface,  and  carries  a  rack  that  engages  the  pinion.  The 
cross  arm  is  assembled  to  the  standard  by  a  stud  and  pin,  is  shaped  to 
receive  the  base  of  the  cross-wire  frame,  has  two  bearings  for  the  cross- 
arm,  and  is  graduated  to  mark  deflections. 

The  cross- wire  frame  carries  four  wires  arranged  to  give  a  small  square 
aperture  in  the  center.  The  lower  part  of  the  frame  has  a  zero  line,  is 
made  to  fit  into  the  cross  arm  and  is  threaded  for  the  screw.  This  last 
is  fixed  in  position,  and  when  rotated  causes  the  cross-wire  frame  to 
move  to  the  right  or  left. 

2.24  inch  6-pounder  Barbette  Mount  (Driggs-Seabury) ,  Model  of 
1898.  The  open  sights  for  this  gun,  with  the  exception  of  minor  and 
unimportant  details,  are  the  same  as  those  given  for  the  4-inch 
Driggs-Schroeder  gun. 

Three-inch,  is-pounder. — The  open  sights  for  these  guns  are  the  bar 
and  drum  pattern,  shown  in  Plate  XV. 

Four-inch  Barbette  Carriage  (Driggs-Schroeder). — The  open  sight 
for  these  guns  consists  of  a  front  sight  screwed  into  its  seat  and  held  by  a 
set  screw.  The  head  of  this  sight  is  a  hoop,  the  single  cross  wires  and 
sighting  point  projecting  from  the  top  of  the  hoop  for  rough  aiming. 
The  rear  sight  is  a  general  pattern  of  bar  sights  moving  in  a  sight  box 
bolted  to  the  face  of  the  breech.  The  right  part  of  the  rear  face  of  the 
bar  has  a  vertical  rack  cut  in  it  throughout  the, length,  in  which  works 
a  small  pinion  controlled  by  a  small  hand  wheel.  The  shaft  of  the  hand 
wheel  carries  a  ratchet  which  normally  engages  in  a  pinion-fixed  ratchet 
in  the  wall  of  the  sight  box,  being  held  in  place  by  a  spring.  The  bar  is 
graduated  in  yards  for  range,  full  charges,  and  set  at  a  vertical  latent 
angle  to  give  an  automatic  correction  for  drift.  To  correct  for  wind  or 
speed  of  target  the  head  of  the  sight  carries  a  cross  bar  actuated  by  a 
worm,  the  cross  bar  being  graduated  in  minutes. 

4.72-and  6-inch  Armstrong  Q.F.  Guns. — The  sights  are  of  the  bar 
and  drum  pattern,  shown  in  Plate  XV,  and  consist  of  a  carrier,  which 
is  fixed  to  two  bosses  on  the  mounting  by  means  of  two  T-headed  bolts; 
a  sight  bar  with  rack  and  front  and  rear  sights;  a  worm  wheel,  pinion 
and  drum  with  graduated  crown  metal  ring  attached  to  the  circumfer- 
ence. The  ring  is  graduated  in  yards.  The  drum  is  fixed  to  the  spindle 
by  means  of  three  screws,  so  as  to  be  readily  moved  round  for  adjustment. 

In  order  to  adjust  the  ring,  slack  the  screws,  run  the  sight  by  means 
of  the  worm  gear  to  the  "  point  blank  "  position,  then  move  the  ring 


INSTRUMENTS,  DEVICES  AND  CHARTS  361 

around  till  the  zero  point  is  in  line  with  the  pointer,  then  tighten  the 
screws. 

The  sight  bar  is  fitted  to  take  the  electric  night  sights.  The  crosshead 
on  the  sight  bar  gives  2  degrees  deflection,  right  and  left,  and  is  fitted 
with  a  screwed  deflection  window  of  H  form,  with  a  horizontal  wire 
stretched  across. 

The  fore  sight  is  furnished  with  an  upright  blade,  terminating  with  a 
spherical  bead. 

Five-inch  Barbette  Carriage  (Model  of  1896). — Sights  for  this  carriage 
consists  of  a  bead  front  sight  and  a  small  ring  set  in  a  window  for  a  rear 
sight.  The  front  sight  is  inserted  in  the  front-sight  bracket  and  the 
bead  is  protected  by  a  ring.  The  rear-sight  window  is  set  in  a  crosshead, 
giving  2  degrees  deflection  right  or  left,  the  smallest  graduation  being 
10  minutes.  The  crosshead  is  on  the  upper  end  of  a  stem  curved  so 
that  in  elevating  the  rear  sight  moves  through  the  arc  of  a  circle,  the 
center  of  which  is  the  bead  of  the  front  sight.  Rack  teeth  are  cut  in  the 
front  face  of  the  stem  and  are  engaged  by  a  worm  operated  by  a  small 
hand  wheel  in  the  rear  of  the  sight  bracket.  This  bracket  carries  a  drum 
graduated  in  yards  and  arranged  to  be  easily  adjusted  so  as  to  bring  its 
zero  to  the  pointer  when  the  sight  is  brought  to  the  "  point  blank  " 
position. 

For  8-,  10-,  and  1 2-inch  B.  L.  Rifles. — All  of  these  guns  are  fitted  for 
axial  sights  arid  are  issued  with  screw  holes  filled  with  brass  plugs.  The 
axial  sights  are  only  issued  for  guns  mounted  on  barbette  carriages. 
These  sights  consist  of  a  simple  notched  rear  sight  without  any  means 
of  elevation  or  deflection,  and  a  point  front  sight. 

TELESCOPIC    SIGHTS 

Three-inch  (is-pounder)  R.  F.  Gun  on  Masking  Parapet  Mount.— 

The  sights  furnished  with  this  mount  are  the  telescopic  sight,  model  of 
1899,  Type  A,  as  shown  in  Fig.  58,  and  the  night  sights. 

The  telescopic  sight  differs  materially  from  all  previous  models.  In- 
stead of  being  pivoted  to  a  trunnion  casting  by  which  it  may  be  adjusted 
in  its  seat  or  bracket  and  which  permits  elevation  to  be  given,  the  tele- 
scope tube  consists  of  a  substantial  bronze  casting  provided  on  its 
under  side  with  two  lugs.  These  lugs  are  about  4  inches  apart  and  rest 
on  and  inclose  the  ends  of  a  flat-machined  seat  on  the  shoulder  bar. 
The  sight  is  secured  in  place  by  two  thumbscrews,  one  on  the  left  side 
of  each  lug,  which  bear  against  the  undercut  side  of  the  seat.  There  are 
no  levels  and  no  movement  of  the  telescope  with  reference  to  its  seat  is 


362 


THE  SERVICE  OF  COAST  ARTILLERY 


possible.  The  telescope  is  used  simply  as  a  more  effective  open  sight, 
elevation  being  given  by  movement  of  the  shoulder  bar. 

The  interior  and  exterior  deflection  scales  and  the  micrometer  head 
on  the  deflection  screw  are  practically  the  same  as  in  the  model  of  1898, 
with  the  exception  of  the  graduation.  Both  scales  are  graduated  to 
2  degrees  30  minutes  on  each  side  of  zero,  the  smallest  division  on  the 
interior  scale  being  6  minutes  and  on  the  exterior  scale  30  minutes. 

One  revolution  of  the  micrometer  head  is  equal  to  1  degree.  The 
6-minute  readings  on  the  outer  scale  are  obtained  from  the  ten  divisions 
on  the  micrometer  head. 


FIG.  58.— Telescopic  Sight,  Type  "A,"  M.  1899,  for  R.-F.  Guns. 

The  telescope  is  provided  with  a  set  of  open  sights  to  serve  as  a  finder. 
The  object  glass  is  protected  by  a  heavy  bronze  disk  attached  to  a 
spindle  about  3^  inches  long,  which  passes  through  a  projection  on  the 
left  side  of  the  telescope  tube  parallel  with  the  axis.  The  rear  end  of 
the  spindle  is  fitted  with  a  short  lever  arm  by  which  the  disk  can  be 
rotated  to  uncover  the  objective. 

Data  for  Telescope 

Field  of  eyepiece 26^° 

Power  of  telescope 3^ 

Field  of  view 7-£-° 

Diameter  of  objective  .;t  ........ 1J  inches 


INSTRUMENTS,  DEVICES  AND  CHARTS 


363 


As  in  the  case  of  the  model  of  1898  the  telescope  is  non-inverting,  but 
the  erect  image  is  obtained  by  the  use  of  an  erecting  eyepiece  instead  of 
prisms.  This  eyepiece  consists  of  three  plano-convex  lenses  mounted 
in  a  brass  tube  which  is  screwed  into  the  main  tube  from  the  rear.  A 
capstan-headed  screw  on  the  right  side  of  the  main  tube  screws  into  a 
collar  in  the  inner  tube  and  determines  the  position  of  the  latter.  The 
sliding  diaphragm  containing  the  cross  hairs  is  placed  in  rear  of  this 
eyepiece. 

Two-inch  Telescopic  Sight,  Model  of  1902. — This  sight  is  shown  in 
detail  in  Fig.  59.  Its  general  description  is  as  follows: 


FIG.  59.— Combination  Open  and  Telescopic  Sight,  2-inch,  M.  1902.     For  R.-F.  Guns. 

The  sight  is  attached  to  the  cradle  by  means  of  a  front  and  rear 
bracket.  The  front  sight  bracket  is  securely  keyed  to  an  extension  of 
the  left  trunnion  of  the  cradle,  and  locked  by  a  screw.  It  is  not  intended 
to  be  removed  except  when  necessary  to  protect  it  from  injury  in  dismounting 
the  shield  or  cradle.  The  rear-sight  bracket  is  attached  to  the  elevating 
rack  bracket  by  means  of  two  0.75-inch  conical  head  screws  and  one 
0.75-inch  headless  screw.  It  is  further  secured  by  a  horizontal  spline 
and  a  vertical  key.  The  front-sight  bracket  is  bored  vertically  at  the 


364  THE  SERVICE  OF  COAST  ARTILLERY 

upper  end  to  receive  the  sight  post.  A  keyway  is  provided  in  the  bracket 
and  a  key  in  the  sight  post  to  prevent  the  latter  turning  in  the  bracket, 
and  the  sight  post  is  provided  with  a  nut  and  locking  pin  at  its  lower 
end.  At  its  upper  end  the  sight  post  is  hinged  to  the  sight  pivot  ty 
means  of  a  bronze  hinge  pin  0.81  inch  in  diameter,  screwed  into  one  of 
the  prongs  of  the  sight  post  and  secured  by  a  taper  pin.  This  hinge  pin 
forms  the  axis  of  rotation  of  the  sight  bar  in  elevation  and  should  never  be 
removed  from  the  sight  post. 

The  upper  end  of  the  sight  pivot  forms  a  seat  for  the  sight-bar  head, 
which  is  drilled  to  slip  over  it  and  is  secured  by  a  nut  with  a  taper  pin 
so  as  to  be  free  to  revolve  around  the  axis  of  the  pivot.  The  sight  pivot , 
therefore,  forms  the  axis  of  rotation  of  the  sight  bar  in  azimuth  and  should 
never  be  removed  from  the  sight  bar  except  when  absolutely  necessary  for 
cleaning  purposes. 

Rear-sight  Bracket. — The  rear  sight  bracket  is  a  steel  forging  which, 
with  its  cover,  a  bronze  casting,  is  milled  out  in  such  a  way  as  to  form 
bearings  for  the  mechanism  necessary  to  elevate  and  depress  the  sight. 
About  half  of  these  bearings  are  in  the  steel  bracket  and  half  in  the 
cover.  Near  the  top  the  sight  bracket  is  bored  to  a  depth  of  1 .752  inches 
and  a  diameter  of  2.35  inches.  The  center  of  this  bore  is  further  drilled 
to  a  depth  of  0.66  inch  and  a  diameter  of  0.625  inch,  the  object  being  to 
form  a  bearing  for  the  sight-elevating  pinion  and  wormwheel.  This 
part,  which  is  of  bronze,  in  one  piece,  is  drilled  0.625  inch  diameter  on 
the  pinion  end.  The  gear  cover  is  milled  to  a  diameter  of  2.35  inches  in 
line  with  the  bore  of  the  sight  bracket,  but  in  the  gear  cover  a  projection 
0.623  inch  in  diameter  and  0.877  inch  long  at  the  center  of  the  bore  is  not 
cut  away  and  forms  the  left-hand  bearing  of  the  sight-elevating  pinion 
and  wormwheel. 

A  horizontal  slot  0.8  inch  wide  and  1.9  inches  deep  is  cut  through  the 
rear-sight  bracket  near  its  middle  part.  Two  bronze  bushings  suitably 
fitted  into  this  slot  form  bearings  for  the  sight-elevating  worm  which 
gears  into  the  worm  wheel  above  described.  A  spline  on  the  gear 
cover  also  fits  into  this  slot  and  helps  to  keep  the  gear  cover  in 
position.  The  sight-elevating  worm  shaft  has  a  hand  wheel  at  each  end. 

A  slot  on  the  proper  radius  is  cut  in  the  gear  cover  for  the  sight-ele- 
vating rack.  At  the  upper  end  of  this  slot,  at  the  rear,  and  on  the  left- 
hand  side  the  gear  cover  is  cut  away  to  make  the  graduations  on  the 
sight-elevating  rack  visible. 

Sight  Holder. — The  sight  holder,  of  bronze,  is  riveted  to  the  rear  end 
of  the  sight  bar  and  forms  an  extension  of  it.  Directly  above  the  sight 
bar  is  the  seat  for  the  telescope,  consisting  of  two  hinged  ring  clamps, 


INSTRUMENTS,  DEVICES  AND  CHARTS  365 

the  forward  one  of  which  is  provided  with  a  slot  to  take  the  spline  of  the 
telescope.  An  extension  of  the  sight  holder  to  the  left  is  bored  and 
tapped  to  receive  the  peep-sight  tube,  consisting  of  a  bronze  tube  with 
an  interior  diameter  of  0.812  inch.  The  peep-sight  plate  is  drilled  at  the 
center  0.125  inch  in  diameter,  forming  the  peep.  It  rests  against  a 
shoulder  of  the  tube,  being  held  in  position  by  a  ring  screwed  into  the 
end  of  the  tube.  It  is  held  and  adjusted  laterally  by  three  screws 
through  the  walls  of  the  tube  bearing  against  its  edges. 

Front  Sight. — The  front  sight  consists  of  a  ring  carrying  two  German 
silver  cross  wires  and  attached  to  a  stem  fitted  with  a  bayonet  joint,  by 
which  it  is  attached  to  the  sight-bar  head. 

Telescope. — The  telescope  consists  of  a  brass  tube  about  16  inches 
long  and  1.78  inches  in  exterior  diameter,  except  at  the  forward  end, 
where  the  tube  is  enlarged  to  an  exterior  diameter  of  2.25  inches,  and 
at  the  two  bearing  surfaces,  where  the  exterior  diameter  is  1.875  inches. 

The  object  glass,  1.75  inches  in  diameter,  held  in  a  brass  ring  with  a 
knurled  head,  is  screwed  into  the  front  end  of  the  tube. 

The  eyepiece  consists  of  two  lenses  held  in  brass  rings  screwed  into 
the  ends  of  a  brass  tube  2.65  inches  long,  which  slides  in  the  rear  end  of 
the  main  tube  of  the  telescope.  This  short  tube  is  slotted  out  at  the  top 
and  is  provided  with  a  rack  placed  at  the  side  of  the  slot.  The  rack 
engages  with  a  pinion  provided  with  a  knurled  head  and  having  its 
bearing  in  the  main  tube  of  the  telescope.  By  turning  the  knurled 
head  the  eyepiece  is  adjusted  for  focus. 

Horizontal  and  vertical  cross  lines  are  etched  upon  the  forward  lens 
of  the  eyepiece  and  scales  for  horizontal  and  vertical  deflection. 

The  horizontal  scale  is  graduated  to  0.05  degree  and  numbered  to 
0.2  degree.  The  vertical  scale  is  graduated  to  0.001  of  the  range  and 
numbered  to  0.004  of  the  range. 

The  distance  between  the  centers  of  the  bearing  surfaces  of  the  tele- 
scope is  6  inches.  The  forward  bearing  surface  is  provided  with  shoul- 
ders to  prevent  longitudinal  motion  in  the  telescope  carrier  and  a  spline 
to  prevent  rotation.  Between  the  two  bearing  surfaces  the  top  of  the 
main  tube  is  slotted  out  to  permit  the  placing  of  a  set  of  Brashear  erect- 
ing prisms.  These  are  held  in  an  adjustable  brass  frame  and  are  covered 
by  a  cap  which  is  screwed  to  the  main  tube  by  six  screws. 

Both  the  object  glass  and  eyepiece  are  protected  by  swinging 
covers. 

For  night  illumination  a  small  tube  for  the  lamp  enters  the  main 
tube  on  the  right-hand  side  just  forward  of  the  front  bearing.  Just  for- 
ward of  this  a  mirror  is  provided,  which,  by  means  of  a  knurled  head, 


366  THE  SERVICE  OF  COAST  ARTILLERY 

can  be  swung  in  or  out  of  the  center  line  of  the  telescope.  Arrows 
on  the  knurled  head  and  on  the  telescope  indicate  when  the  mirror  is 
in  the  axis  of  the  telescope. 

Two-inch  Telescopic  Sight  (Model  of  1906). — This  sight  is  designed 
for  use  on  the  15-pounder  R.F.  gun,  model  of  1903.  It  consists  of  a 
telescope,  sight  bracket,  cradle,  with  the  open-sight  attachments  con- 
sisting of  the  sight  shank,  deflection  worm  box  and  head  of  shank,  range 
drum,  gear  cast  cover  and  cover  for  range  drum,  elevating  worm,  the 
fulcrum,  the  yoke,  deflection  scale,  elevating-gear  shaft  and  necessary 
lighting  cables. 

The  sight  bracket  is  bolted  to  the  carriage  at  its  lower  end.  The 
cradle  is  assembled  at  the  forward  end  of  the  front-sight  bracket  by 
means  of  the  fulcrum,  the  fulcrum  axis  for  bearings  in  the  two  sides  of 
the  front  sight  bracket  permitting  rotation  for  elevation  and  deflection, 
and  the  fulcrum  is  a  short  vertical  shaft  on  its  outside  to  which  the  for- 
ward end  of  the  cradle  is  assembled  so  as  to  allow  rotation  in  azimuth. 
At  the  rear  end  the  cradle  is  assembled  to  the  sigl^t  shank  by  means  of 
the  sight-shank  head  and  the  deflection  worm.  The  latter  is  seated  in 
the  sight-shank  head,  which  thus  forms  the  deflection-worm  box  and 
meshes  into  a  worm  segment  cut  in  the  cradle.  The  front  and  rear  faces 
of  the  deflection  box  and  the  head  of  the  sight  shank  are  arcs  of  circles 
having  their  common  center  on  the  axis  of  the  vertical  shaft  fulcrum. 

The  elevation  of  the  sight  and  the  rotation  of  the  range  drum  are 
accomplished  by  the  elevating  gear,  consisting  of  the  elevating  worm, 
elevating-gear  shaft  with  its  worm  gear  and  spur-  gear,  the  latter  two 
being  in  one  piece.  The  elevating  worm  engages  the  worm  gear  and  the 
spur  gear  engages  the  sight-shank  rack.  The  piece  on  which  these  two 
gears  are  mounted  is  cut  on  a  square  section  of  the  elevating-gear  shaft, 
which  is  also  the  range-drum  shaft,  the  range  drum  being  mounted  and 
held  in  place  by  the  friction  of  a  washer  bearing  against  the  drum  and 
the  friction  of  the  drum  on  a  shoulder  of  the  shaft.  A  German  silver 
ribbon  spring  about  eleven  feet  long  is  secured  at  one  end  to  the  ele- 
vating-gear shaft  and  is  wound  several  times  around  the  shaft,  and  has 
the  other  end  secured  to  the  gear-case  cover. 

By  rotating  the  elevating  worm  the  elevating-gear  shaft  is  moved, 
adding  to  or  releasing  the  tension  on  the  spring,  at  the  same  time  de- 
pressing or  elevating  the  cradle  by  means  of  the  sight  shank  also  rotating 
the  range  drum.  The  object  of  the  spring  is  to  equalize  the  force  re- 
quired to  depress  or  elevate  the  cradle.  A  range  pointer  is  attached  to 
the  cover,  which  is  bolted  to  the  sight  bracket.  The  elevation  scale  is 
of  German  silver  dovetailed  into  the  rear  face  of  the  sight  shank,  and 


INSTRUMENTS,  DEVICES  AND  CHARTS 


367 


reads  from  zero  to  16  degrees,  the  least  reading  being  6  minutes,  or 
.10  of  a  degree. 

The  range  pointer  is  a  piece  of  German  silver  dovetailed  into  the  gear- 
case  cover  just  opposite  the  lamp  bracket  and  the  range-drum  elevation 
scale.  The  deflection  scale,  of  German  silver,  is  dovetailed  into.the  rear 
end  of  the  cradle.  The  numbers  on  the  scale  are  reference  numbers, 
three  (3)  representing  the  original  or  central  position  of  the  scale.  The 
interval  between  whole  numbers  is  equal  to  one  degree  of  arc.  The 
lowest  reading  of  the  scale  is  6  minutes,  or  .10  of  a  degree. 

The  deflection  scale  index  is  cut  on  a  German  silver  plate,  secured  to  a 
lug  projecting  from  the  rear  of  the  sight  shank.  The  principal  parts  of 


OBJECTIVE 
CELLS  AND  RING 


LAMP  BRACKET  FOR 
ILLUMINATING  CROSS  WIRES 


EYE  PIECE.  FIELI 
AND  EYE  LENS 


FIG.  59A. — 2-inch  Telescopic  Sight,  M.  1906,  for  3-inch  R.-F.  Guns. 

the  telescope  are  the  tube,  the  objective,  the  Porro  erectingvprisms,  the 
draw  tube,  cross- wire  holder,  the  focusing  sleeve,  the  focusing  ring  and 
the  eyepiece. 

The  telescope  is  shown  in  Fig.  59A.  The  telescope  is  secured  in  position 
on  four  accurately  bored  projections  on  the  cradle  by  the  front  and  rear 
telescope  clamps,  each  of  which  is  machine-finished  to  proper  bearing 
on  the  upper  portion  of  the  telescope  to  secure  proper  alignment  of  the 
optical  axis  and  to  insure  the  vertical  wires  being  held  vertically.  The 
telescope  has  a  2-inch  aperture.  The  magnifying  power  of  the  eyepiece 
is  8  and  the  sight  has  a  field  of  4^  degrees. 

Three-inch  Telescopic  Sight  (Model  of  1904). — This  sight  is  shown 
in  Plate  XXXIII  and  is  designed  for  use  either  on  barbette  or  disap- 
pearing carriages. 


368  THE  SERVICE  OF  COAST  ARTILLERY 

Sights  for  Barbette  Carriages. — The  principal  parts  are  the  telescope, 
the  sight  bracket,  the  cradle,  the  open  sights,  the  sight  shank  with  de- 
flection-worm box  and  head  of  sight  shank,  the  range  drum,  the  gear- 
case  cover  and  cover  for  range  drum,  the  elevating  worm,  the  fulcrum, 
the  yoke^  the  cables  and  electric  lamps,  the  deflection  scale,  the  elevation 
scale,  the  deflection  worm  and  the  elevating  gear  shaft. 

The  sight  bracket  is  bolted  to  the  carriage  by  means  of  the  feet.  The 
cradle  is  assembled  at  the  forward  end  to  the  sight  bracket  by  means  of 
the  yoke  and  fulcrum.  The  yoke  shaft  seats  in  the  sight  bracket  and  is 
keyed  in  place;  the  fulcrum  axes  have  bearings  in  the  two  sides  of  the 
yoke  permitting  rotation  for  elevation  and  depression,  and  the  fulcrum 
has  a  short  vertical  shaft  on  its  under  side  to  which  the  forward  end  of  the 
cradle  is  assembled  so  as  to  allow  rotation  in  azimuth  only.  At  the  rear 
end  the  sight  shank  is  assembled  between  the  sight  bracket  and  the  gear- 
case  cover,  being  held  in  place  by  the  gear-case  cover  and  the  elevating 
gearing.  The  cradle  is  assembled  to  the  sight  shank  by  means  of  its 
head  (which  is  also  the  deflection-worm  box)  and  the  deflection  worm, 
the  latter  being  seated  in  the  box  and  meshing  into  a  worm  segment  cut 
in  the  cradle.  The  front  and  rear  faces  of  the  deflection  box  and  head 
of  sight  shank  are  arcs  of  circles  having  their  common  center  on  the 
axis  of  the  vertical  shaft  of  the  fulcrum,  and  the  front  and  rear  faces  of 
the  sight  shank  and  its  seat  are  arcs  of  circles  having  their  common 
center  on  the  central  line  of  the  fulcrum  axes. 

The  elevation  of  the  sight  and  the  rotation  of  the  range  drum  are 
accomplished  by  the  elevating  gearing,  consisting- of  the  elevating  worm 
and  the  elevating-gear  shaft  with  its  worm  gear  and  spur  gear,  the  latter 
two  being  on  one  piece.  The  elevating  worm  engages  the  worm  gear 
and  the  spur  gear  engages  the  sight-shank  rack.  The  piece  on  which 
these  two  gears  are  cut  is  mounted  on  a  squared  section  of  the  elevating- 
gear  shaft,  which  is  also  the  range-drum  shaft.  The  range  drum  is  also 
mounted  on  this  shaft  and  is  held  in  place  by  the  friction  of  a  nut  on  a 
washer  bearing  against  the  drum  and  the  friction  of  the  drum  on  a 
shoulder  of  the  shaft.  A  ribbon  spring  11  feet  long  and  of  German 
silver  is  secured  at  one  end  to  the  elevating-gear  shaft,  is  wound  several 
times  around  the  shaft,  and  has  the  other  end  secured  to  the  gear-case 
cover.  The  cover  is  bolted  to  the  sight  bracket.  By  rotating  the  ele- 
vating worm,  the  elevating-gear  shaft  is  turned,  adding  to  or  releasing 
tension  on  the  spring,  depressing  or  elevating  the  cradle  by  means  of 
the  sight  shank  and  rotating  the  range  drum.  The  spring  serves  to 
equalize  the  force  required  to  depress  and  elevate  the  cradle.  The  gear- 
case  cover  and  the  bracket  serve  to  protect  the  elevating  gearing,  the 


INSTRUMENTS,  DEVICES  AND  CHARTS  369 

spring,  and  the  range  drum.  The  range-scale  pointer  is  attached  to 
the  cover. 

The  elevation  scale  is  of  German  silver,  is  dovetailed  into  the  rear  face 
of  the  sight  shank,  and  reads  to  6  minutes  from  zero  to  16  degrees.  The 
pointer  is  on  a  piece  of  German  silver  dovetailed  into  the  sight  bracket 
just  opposite  the  lamp  bracket  for  range  drum  and  elevation  scale. 

Deflection  is  obtained  by  rotating  the  deflection  worm  which  is  seated 
in  the  deflection-worm  box  and  meshes  into  a  worm  segment  cut  into  the 
cradle  where  the  box  is  seated. 

The  deflection  scale,  of  German  silver,  is  secured  to  the  rear  end  of 
the  cradle  and  reads  to  0.05  of  a  degree,  which  equals  3  minutes,  over 
an  arc  of  4  degrees,  beginning  with  1  degree  on  the  right.  The 
3-degree  mark  gives  no  deflection.  The  pointer  plate  is  secured  to  a 
bracket  which  is  screwed  to  the  under  side  of  the  sight  shank  head.  This 
bracket  has,  at  the  rear  end,  the  deflection  lamp  bracket  and  a  lug  that 
works  in  a  groove  in  the  end  of  the  cradle. 

The  open  sight  consists  of  a  peep  sight  in  rear  and  a  cross  sight  in 
front,  the  former  mounted  on  the  eye  and  telescope  clamp,  and  the  latter 
on  the  cross-sight  holder.  It  is  for  use  in  picking  up  an  object  quickly. 

Each  sight  is  provided  with  three  small  electric  lamps  of  about  2 
candlepower;  those  originally  furnished  with  the  first  405  sights  have 
a  voltage  of  3.75  to  4.75,  and  an  amperage  from  0.75  to  1,  while  those 
that  will  be  used  for  replacements  and  for  sights  to  be  manufactured 
have  the  voltage  from  5.5  to  6.5,  with  an  amperage  from  1.25  to  1.35. 
One  of  these  lamps  illuminates  the  cross  wires,  giving  bright  lines  in  a 
dark  field,  and  the  other  two  illuminate  the  scale  pointers  and  adjacent 
parts  of  the  scales.  They  are  connected  with  the  electric  circuit  by  the 
cables  and  plug  connections.  The  lamp  that  illuminates  the  cross  wires 
is  placed  in  a  holder  that  is  screwed  to  the  eye  end  of  the  telescope  tube 
on  the  right-hand  side.  Two  small  mirrors  deflect  the  rays  of  light 
through  two  elongated  openings  cut  through  the  telescope  tube  90  de- 
grees apart.  These  openings  are  so  arranged  that  the  light  from  each 
mirror  is  thrown  upon  the  full  length  of  the  wire  opposite. 

The  principal  parts  of  the  telescope  are  the  telescope  tube,  the  objec- 
tive, the  Porro  erecting  prisms,  the  draw  tube,  the  cross- wire  ring,  the 
adjusting  sleeve,  the  adjusting  ring,  and  the  eyepiece. 

The  telescope  tube  is  the  principal  piece  to  which  the  other  parts  are 
assembled.  The  objective  is  triple,  is  seated  in  a  cell  that  screws  into 
the  forward  end  of  the  telescope  tube,  and  gives  a  3-inch  clear  aperture. 
The  Porro  erecting  prisms  are  two  in  number,  secured  in  place  by  a 
bronze  frame.  There  are  no  cemented  surfaces,  as  in  the  Brashear- 


370  THE  SERVICE  OF  COAST  ARTILLERY 

Hastings  prisms  used  in  former  types,  which  reduces  the  chance  of  injury, 
renders  replacement  easier,  and  facilitates  cleaning. 

The  cross  wires  are  secured  to  a  ring  by  four  clamps,  and  are  at  right 
angles  to  each  other.  The  cross-wire  ring  is  carried  in  a  holder  which  is 
secured  to  the  draw  tube  by  screws.  The  draw  tube  is  assembled  to  the 
focusing  sleeve  so  as  to  allow  longitudinal  motion  of  the  former  when 
the  focusing  ring  is  rotated,  and  to  force  rotation  of  the  tube  when  the 
focusing  sleeve  is  rotated.  The  sleeve  is  screwed  into  the  rear  end  of  the 
telescope  tube  by  a  thread  of  tight  fit,  so  that  it  is  difficult  to  rotate. 
The  focusing  ring  is  seated  on  the  focusing  sleeve  by  a  threaded  surface, 
its  motion  being  limited  by  the  telescope  tube  in  front  and  the  focusing 
sleeve  nut  in  rear.  When  turned,  it  transmits  to  the  draw  tube  and 
reticule  its  longitudinal  motion  only. 

The  eyepiece  consists  of  the  eyepiece  tube,  the  field  lens,  the  eye  lens 
in  its  holder,  and  the  eye-lens  cover.  The  eyepiece  tube  is  screwed  into 
the  draw  tube  and  carries  the  field  lens  and  the  eye  lens  with  its  holder, 
the  cover  being  screwed  to  the  latter.  There  is  an  amber  glass  shade  in 
a  holder  that  is  pivoted  so  that  it  may  be  used  or  not,  as  desired,  and 
which  is  provided  to  protect  the  eye  from  a  glare  of  light.  The  eyepiece 
serves  to  magnify  the  image  at  the  cross  wires  and  to  concentrate  the 
rays  of  light  in  the  eye. 

The  front  end  of  the  telescope  is  provided  with  a  movable  shutter  for 
the  protection  of  the  objective. 

The  clear  aperture  of  the  telescope  is  3  inches,  the  focal  length  is 
17.25  inches,  the  magnifying  powers  of  the  two  eyepieces  are  12  and  20 
diameters  and  the  fields  are  3.6  degrees  for  the  12-power  eyepiece  and 
2.6  degrees  for  the  20-power. 

The  image  is  direct,  the  erecting  being  secured  by  the  Porro  prisms, 
each  of  which  twice  totally  deflects  the  rays  of  light  at  an  angle  of  90 
degrees  so  that  it  emerges  parallel  to  the  entering  ray  and  in  the  original 
direction.  The  paths  of  two  rays  of  light  are  shown  in  Fig.  47,  giving 
an  illustration  of  the  erecting  process,  in  which,  however,  the  90-degree 
angles  are  not  all  projected  as  90  degrees,  because  of  the  relative  posi- 
tions of  the  prisms.  The  eyepiece  of  power  12  should  generally  be  used, 
as  the  higher  power  so  magnifies  the  particles  in  the  atmosphere  as 
to  cause  blurring  on  any  but  a  dark  -day. 

The  telescope  is  secured  in  position  by  six  accurately  bored  projec- 
tions, four  on  the  cradle  and  one  on  each  clamp.  A  locating  lug  on  the 
front  clamp  fits  into  a  recess  on  the  telescope,  thus  bringing  the  vertical 
wire  plumb. 

For  those  carriages  in  which  the  gun  is  carried  in  a  cradle,  the  sight 


INSTRUMENTS,  DEVICES  AND  CHARTS  371 

bracket  is  bolted  by  means  of  the  feet  to  seats  which  form  parts  of  the  gun 
cradle,  and  when  the  sight  is  properly  assembled  to  the  carriage  and  the 
elevation  and  deflection  readings  are  zero,  the  optical  axis  of  the  tele- 
scope and  the  axis  of  the  bore  of  the  gun  will  remain  parallel  at  all  ele- 
vations. Therefore,  if  the  sight  be  set  at  the  elevation  required  for  the 
range  of  the  object  to  be  fired  at,  and  then  be  laid  upon  it,  the  gun  will 
automatically  receive  the  same  elevation.  Since  the  deflection  move- 
ment of  the  sight  is  independent  of  the  gun,  and  deflection  necessary 
may  be  given  without  affecting  the  elevation. 

The  sight  brackets  for  barbette  carriages  are  lefts  and  rights. 


SIGHTS    FOR    DISAPPEARING    CARRIAGES 

The  sights  for  disappearing  carriages  differ  from  those  for  barbette 
in  that  they  are  all  alike  for  the  same  type  of  carriage  (the  range  drums 
all  being  on  the  left  side) ;  a  sight  arm  is  substituted  for  the  sight  bracket, 
and  a  different  method  of  attachment  is  used. 

The  sight  arm  differs  from  the  sight  bracket  in  shape,  has  an  elevation 
guide,  and  the  feet  of  the  sight  bracket  are  replaced  by  seats  for  two  pins. 

Disappearing  carriages,  after  model  of  1901,  are  supplied  with  two 
sight  standards,  one  right  and  one  left.  The  elevating  mechanism  for 
the  gun  may  be  operated  by  a  handwheel  assembled  to  the  left  end  of 
the  elevating  shaft,  which  is  supported  by  a  bracket  attached  to  the  left 
sight  standard.  This  shaft  connects  through  bevel  gearing  with  an  in- 
clined shaft  (passing  through  the  sight  standard),  the  upper  end  of 
which  connects  by  bevel  gearing  with  a  third  shaft  that  carries  a  maneu- 
vering handwheel.  The  middle  portion  of  the  inclined  shaft  is  threaded, 
and  carries  a  nut  to  which  is  attached  a  sight-elevating  arm,  the  upper 
end  of  which  is  a  swivel  fork.  The  top  of  the  sight  arm  ends  in  a  hori- 
zontal flange  surmounted  by  a  cylindrical  axis,  upon  which  is  centered 
a  sight-arm  bracket,  with  a  flange  resting  upon  the  flange  of  the  sight 
standard.  This  bracket  has  a  small  motion  in  azimuth  and  can  be  set 
in  its  proper  position  by  lugs  and  adjusting  screws,  then  clamped  by  screw 
bolts  passing  through  its  flange  and  into  that  of  the  sight  standard. 
The  bracket  has  two  arms  extending  forward,  and  the  sight  arm  is 
assembled  between  them  by  a  pin  passing  through  the  front  ends  of  the 
two  arms  of  the  bracket  and  the  front  seat  in  the  sight  arm.  The  sight- 
elevating  arm  passes  through  the  bottom  of  the  bracket  and  is  assembled 
to  the  sight  arm  by  a  pin  passing  through  the  sight  arm  and  the  fork  of 
the  sight-elevating  arm.  The  sight-arm  bracket  has  two  guide  ways, 


372  THE  SERVICE  OF  COAST  ARTILLERY 

between  which  travels  the  elevation  guide  of  the  sight  arm.  The  ele- 
vating shaft  operates  the  elevating  *screw,  on  which  travels  a  slide  to 
which  the  elevating  arm  is  pivoted  at  one  end,  the  other  end  being 
pivoted  to  a  band  on  the  breech  of  the  gun.  The  inclined  shaft  is  in  two 
pieces,  joined  by  a  coupling,  so  that  the  gun  and  telescope  can  be  set 
independently  and  the  connection  can  afterwards  be  made. 

The  relations  of  the  pitches  of  threads,  the  number  of  teeth  in  gears 
and  pinions,  the  angles  of  the  elevating  screw  and  the  inclined  shaft,  and 
the  lengths  of  parts  are  of  such  that,  if  the  optical^axis  of  the  telescope 
and  the  axis  of  the  bore  of  the  gun  be  set  parallel  at  zero  elevation  and 
deflection,  they  will  so  remain  at  any  elevation.  Rotating  either  hand- 
wheel  elevates  or  depresses  the  gun  and  the  sight  arm  at  the  same  time 
and  through  equal  angles.  Therefore  the  principles  of  operating  the 
sight  are  the  same  as  already  described  for  barbette  carriages. 

The  right  sight  is  mounted  similarly  to  the  left,  except  that  it  has  no 
connection  with  the  elevating  mechanism  of  the  carriage,  the  rear  of 
the  sight  arm  being  assembled  by  a  pin  passing  through  it  and  two  lugs 
on  the  sight-arm  bracket.  This  sight  can  be  used  only  for  following  an 
object  in  azimuth,  since  the  sight  arm  remains  stationary. 

SIGHTS  OF  NEARLY  SAME  DESIGN  AS  MODEL  OF  1904 

There  are  in  service  26  sights,  numbered  from  1  to  26,  both  inclusive, 
which  are  nearly  the  same  as  those  described  above.  The  differences 
are  due  to  substituting  in  the  latter  Porro  double  reflecting  prisms  for 
the  Brashear-Hastings  erecting  prisms  used  in  the  former. 

The  telescopes  of  these  sights  are  differently  shaped  from  the  model  of 
1904,  being  practically  symmetrical  about  the  axis;  they  are  longer  by 
about  3J  inches,  the  peep  sight  is  directly  over  the  eyepiece,  the  rear 
clamp  is  differently  shaped,  the  sides  upon  which  the  shutter  and  clamps 
are  hinged  have  been  reversed,  the  adjusting  arrangements  for  the  cross- 
wire  ring  are  different,  and  the  diameters  of  bearings  on  the  telescopes 
and  cradles  for  seating  the  telescope  are  ^  inch  smaller  than  on  the 
model  of  1904. 

METHOD    OF    ASSEMBLING    SIGHTS    AND    LOCATING    POINTERS 

For  Barbette  Carriages. — In  assembling  the  brackets  for  the  barbette 
carriages,  great  care  should  be  taken  to  see  that  the  seats  are  level  in  both 
directions,  and  that  burrs,  paint,  and  rust  are  removed  from  them  and 
the  feet  of  the  brackets.  A  small  obstruction  of  this  kind  will  throw  the 


INSTRUMENTS,  DEVICES  AND  CHARTS  373 

sight  shank  out  of  plumb.  In  setting  up  the  bolts,  all  should  be  brought 
to  a  firm  bearing  before  any  are  set  up  tight. 

Neither  the  elevation  nor  the  deflection  pointer  is  marked  by  the 
manufacturer  of  the  sights,  since  there  is  no  adjustment  for  either  on 
the  carnage.  The  elevation  pointer  should  be  cut  at  the  works  of  the 
builder  of  the  carriage  to  allow  for  any  possible  inaccuracy  in  the  seats 
and  the  deflection  pointer  should  be  put  on  at  the  emplacement  after 
the  gun  is  mounted. 

After  the  sight  is  assembled  to  the  carriage  and  while  the  gun  is  at 
zero  elevation  the  sight  should  be  accurately  leveled  and  the  pointer  cut 
exactly  opposite  the  zero  of  the  elevation  scale. 

The  position  of  the  deflection  pointer  may  be  determined  by  setting 
up  two  screens  at  right  angles  to  the  axis  of  the  gun,  one  more  distant 
from  it  than  the  other,  and  measuring  the  horizontal  distance  on  each 
screen  between  the  points  in  which  the  line  of  sight  and  the  axis  of  the 
bore  intersect  it.  When  these  two  distances  are  equal,  the  vertical 
planes  through  the  line  of  sight  and  the  axis  of  the  bore  are  parallel  arid 
the  pointer  should  be  cut  exactly  opposite  the  3-degree  mark  on  the 
deflection  scale. 

For  Disappearing  Carriages. — The  elevation  pointer  should  be  cut 
at  the  emplacement,  and  both  sights  should  have  the  work  done  while 
mounted  on  the  left  sight  standard.  The  gun  and  the  sight  should  be 
leveled  accurately  and  independently,  and  the  pointer  should  then  be 
cut  exactly  opposite  the  zero  elevation  scale,  the  set  screw  of  the  coupling 
having  been  previously  seated  and  the  coupling  clamped.  The  elevating 
mechanism  of  the  carriage  should  be  so  marked  by  the  builder  that  it  can 
be  assembled  with  all  parts  in  correct  relation  without  leveling. 

The  deflection  pointer  is  cut  by  the  manufacturer  of  the  sight,  but  the 
vertical  planes  of  the  line  of  sight  and  the  axis  of  the  bore  of  the  gun 
should  be  brought  parallel  at  the  emplacement,  using  some  method  such 
as  outlined  for  barbette  sights  and  rotating  the  sight-arm  bracket  with 
the  deflection  pointer  set  at  the  3-degree  mark.  When  the  sight  is  in 
the  correct  position,  the  bracket  should  be  clamped  and  a  light  line  cut 
so  as  to  extend  over  both  the  flange  on  the  bracket  and  that  on  the  sight 
standard.  The  sight  for  each  side  of  a  carriage  should  be  set  on  its  own 
sight  standard. 

The  range  drum  for  all  sights  must  be  graduated  after  the  height  of 
the  emplacement  above  sea  level  is  known. 

Adjustments. — The  cross  wires  are  rendered  distinct  by  screwing  the 
eyepiece  in  or  out,  and  this  adjustment  has  no  other  object.  If  the  tele- 
scope is  frequently  used  by  the  same  observer,  the  eyepiece  can  be  reset 


374  THE  SERVICE    COAST  ARTILLERY 

at  the  correct  position  by  using  the  graduations  on  the  outer  rim  in  con- 
nection with  the  pointer  on  the  focusing-sleeve  nut.  After  bringing  the 
cross  wires  into  distinct  vision  by  adjusting  the  eyepiece,  the  wires  may 
be  brought  into  the  focal  plane  by  turning  the  focusing  ring  until  the 
object  appears  distinctly  and  does  not  seem  to  shift  when  the  eye  is 
moved  from  side  to  side  of  the  eyepiece.  This  adjustment  is  impossible 
if  the  object  is  too  close  to  the  telescope'  100  yards  is  usually 
sufficient. 

The  cross  wires  may  be  adj  usted  to  bring  them  into  vertical  and  hori- 
zontal planes  by  removing  the  focusing-sleeve  nut,  unscrewing  the  focus- 
ing ring  until  spanner  holes  appear  in  the  focusing-sleeve,  placing  a 
spanner  wrench  in  the  holes  and  tapping  the  handle  of  the  wrench  with 
a  very  light  hammer.  This  adjustment  should  be  made  with  the  tele- 
scope in  the  cradle  and  trained  on  a  plumb  line,  and  only  those  thoroughly 
familiar  with  the  instrument  should  attempt  it. 

The  adjustment  of  the  cross  wires  of  the  sights  numbered  from  1  to  26 
is  made  by  unscrewing  the  focusing-sleeve  nut  and  the  focusing  ring  until 
access  is  given  to  the  capstan-head  adjusting  screws  that  secure  the 
cross-wire  ring.  These  screws  should  be  loosened  the  adj  ustment  made 
and  the  screws  again  set  up. 

To  adjust  the  tension  of  the  range-drum  spring,  run  the  sight-shank 
rack  out  of  mesh,  turn  the  balanced  handwheel  to  the  right  to  relievo 
tension  or  to  the  left  to  increase  tension  and  re-engage  the  rack.  When 
the  cradle  and  telescope  are  in  place  and  the  elevation  is  8  degrees,  the 
force  required  to  rotate  the  handwheel  should  be  the  same  for  both 
directions.  This  adjustment  must  never  be  made  after  the  drum  is 
graduated,  and  the  cradle  must  first  be  disengaaed  from  the  head  of  the 
sight  shank. 

Care  and  Preservation. — Telescopic  sights  are  necessarily  delicate 
instruments  and  must  not  be  subjected  to  rough  usage,  jars,  or  strains. 
When  not  in  use,  the  telescope  should  be  kept  in  its  leather  case  and 
should  be  stored  in  a  dry  place.  It  should  be  occasionally  examined  to 
insure  its  not  being  corroded  by  tannic  acid  from  the  case  and  all  traces 
of  dust  or  moisture  should  be  removed  before  putting  it  away. 

To  obtain  satisfactory  vision,  the  glasses  should  be  kept  perfectly 
clear  and  dry.  In  case  moisture  collects  on  the  glasses,  place  the  tele- 
scope in  a  gentle  warmth;  this  is  usually  sufficient  to  remove  it.  A 
piece  of  chamois  skin  or  a  clean  linen  handkerchief  will  answer  for  clean- 
ing purposes,  care  being  taken  that  the  cleaning  material  does  not  contain 
any  dirt  or  grit.  The  glasses  will  seldom  require  cleaning  on  the  inside; 
but,  when  necessary,  they  should  be  unscrewed,  and  by  a  competent 


INSTRUMENTS,  DEVICES  AND  CHARTS  375 

person  only.  The  object  glass  must  always  be  kept  screwed  home,  except 
when  removed  for  cleaning. 

The  erecting  prisms  should  not  be  removed,  except  by  an  optician, 
and  if  they  need  repair,  report  should  be  made  to  the  proper  authority. 
Removal  is  apt  to  disturb  the  adjustment,  and  finger  marks  or  lint  will 
cause  difficulty. 

The  cross  wires  are  unprotected  when  the  eyepiece  is  removed,  and 
great  care  must  be  exercised  not  to  touch  them,  as  they  are  very  delicate. 
No  attempt  should  be  made  to  clean  them,  except  by  blowing. 

The  sight  bracket  (or  arm)  and  cradle  should  never  be  removed  from 
the  carriage  unless  the  carriage  is  dismounted.  When  not  in  use  these 
parts  should  be  kept  covered  by  hoods  provided  for  the  purpose.  All 
bright  parts  should  be  kept  thoroughly  oiled,  special  care  being  given 
to  the  worm  box,  sight  shank,  and  bearings  for  the  telescope,  which  are 
of  steel.  Care  should  be  taken  not  to  remove  the  oil  in  putting  on  the 
hood.  The  oil  should  be  wiped  off  before  use.  The  hood  should  be  re- 
moved and  the  sight  brackets  (or  arms),  etc.,  examined  at  least  once  in 
every  two  weeks,  and  tho  cradle  should  be  removed  in  elevation  and 
deflection  so  that  as  much  as  possible  of  the  sight  shank  and  worm  box 
can  be  inspected. 

Special  care  should  be  taken  in  the  use  of  the  three  small  electric 
lamps,  as  they  are  fragile.  The  resistance  should  be  carefully  regulated, 
since  a  small  increase  in  voltage  will  burn  them  out.  It  is  desirable  to 
first  throw  in  a  comparatively  large  resistance  and  then  adjust  until  the 
proper  illumination  is  obtained.  Each  lamp  should  seat  in  its  receptacle 
not  less  than  one  and  one-half  turns. 

The  Scott  Telescopic  Sight. — The  telescopic  sights  in  service  are  the 
model  of  1896  Mi,  the  model  of  1897,  the  model  of  1898,  and  the  model 
of  1898  M.  See  Plate  XXXIV. 

These  sights  consist  of  a  telescope  mounted  on  an  adjustable  frame 
on  which  are  trunnions  and  a  projecting  lug  by  which  the  sight  and  its 
frame  are  attached  to  either  a  gun  or  gun  carriage  by  means  of  a  bracket 
or  sight  holder. 

For  attaching  the  sight  to  a  gun  a  trunnion  bracket  is  fastened  to  the 
right  trunnion  in  which  the  sight  frame  is  placed  and  secured  so  as  to 
hold  the  telescope  during  the  shock  of  discharge. 

For  attaching  the  sight  to  a  barbette  carriage  a  sight  bracket  is  fast- 
ened to  the  rear  part  of  the  right  chassis.  The  upper  end  of  this  bracket 
has  a  vertical  face,  to  which  is  attached  the  sight  bracket  which  holds 
the  sight  and  its  frame. 

Disappearing  carriages  are  provided  with  sight  standards  attached  to 


376  THE  SERVICE  OF  COAST  ARTILLERY 

either  the  right  or  left  chassis  rail.  On  the  upper  part  of  the  standard 
are  two  lugs,  slotted  to  receive  the  sight  holder.  The  outsides  of  these 
slots  are  closed  with  caps,  in  each  of  which  is  a  clamping  screw  for  se- 
curing the  sight  holder  when  adjusted  to  a  convenient  height  for  the 
gunner.  The  upper  end  of  the  sight  holder  is  arranged  to  receive  the 
sight  and  its  frame. 

A  catch  band  is  placed  on  the  models  of  1898  and  1898  M  sights,  to 
which  the  end  of  the  retainer  is  secured.  With  the  models  of  1896  Mi 
and  1897  sights  the  end  of  the  retainer  is  secured  to  the  lower  bar  of  the 
sight  frame. 

The  line  passing  through  the  centers  of  the  trunnions  is  called  the  axis 
of  revolution  of  the  sight  or  the  axis  of  the  sight  trunnion,  and  is  parallel 
to  the  optical  axis  of  the  telescope  at  zero  elevation. 

The  sight  bracket,  which  is  the  same  for  all  models  of  sights,  is  pro- 
vided with  two  V's  and  a  leveling  screw.  The  sight  trunnion  is  seated 
in  the  V's  and  the  leveling  lug  between  them  bears  against  the  leveling 
screw.  The  latter,  working  against  the  lug,  levels  the  sight. 

The  overbalancing  of  the  sight  and  the  method  of  suspension  to  the 
bracket  enable  the  sight  to  be  used  for  reverse  laying.  The  undercut  in 
the  cross  level  exposes  the  bubble  for  adjustment. 

A  strap  fastened  loosely  to  the  frame  is  used  for  carrying  the  sight. 

For  each  sight  there  is  provided  a  leather  case  in  which  the  sight  is 
carried  and  kept. 

Telescopic  Sight,  Model  of  1896  Ml,  consists  Of  a  telescope  carried 
by  an  adjustable  frame,  as  above  described.  The  telescope  is  supported 
by  having  its  forward  end  pivoted  and  secured  to  the  frame,  while  the 
other  end  has  a  sliding  motion  along  the  elevation  arc,  through  contact 
with  the  vernier  piece.  The  telescope  is  an  ordinary  non-inverting  one, 
provided  with  an  achromatic  objective  composed  of  two  lenses  in  contact 
and  a  Ramsden  eyepiece  to  magnify  the  image  formed  by  the  objective. 

The  non-inverting  telescope  is  obtained  by  inserting  the  Hastings- 
Brashear  compound  erecting  prism  between  the  sliding  diaphragm 
and  the  objective.  This  compound  prism  consists  of  two  prisms 
having  angles  of  30°,  60°,  and  90°,  laid  with  their  30°  angle  toward 
each  other  on  a  parallel-sided  glass  plate,  and  on  the  other  side  of 
this  plate  is  laid  a  third  prism  having  a  true  90°  angle.  Successive 
reflections  at  the  surfaces  of  these  three  prisms  erect  the  image  with- 
out any  lateral  displacement  of  the  rays  of  light  other  than  that 
necessary  for  the  purpose,  and  without  lengthening  the  telescope 
tube,  or  diminishing  the  field  of  view.  This  compound  prism  is 
mounted  in  a  frame  provided  with  two  sets  of  screws  by  means  of 


PLATE  XXXIV 


DEFLECTION  SCALE 

OF  DEGREES  AND 

HALF  DEGREES 


Telescopic  Sight,  M.  1898  Mn.     Mounted  on  Hagood  Tripod  Mount. 


INSTRUMENTS,  DEVICES  AND  CHARTS  377 

which  it  is  adjusted  after  being  assembled  in  the  telescope.  Just 
forward  of  the  sliding  diaphragm  the  telescope  tube  is  cut  away  on 
top  to  admit  the  prism  and  its  frame.  Two  screws  passing  through 
flanges  on  the  latter  secure  it  to  the  tube  and  determine  its  position. 
A  roof-shaped  plate  screwed  to  the  telescope  tube  protects  the  prism 
from  dust  or  mechanical  injury. 

Mechanism  of  the  Telescope. — Within  the  telescope  is  a  sliding 
diaphragm  or  frame  carrying  a  vertical  platinum  cross  wire  0.001  inch 
in  diameter;  also  a  thin  glass  reticule,  a  horizontal  and  a  vertical 
scale;  also  a  horizontal  line  which  takes  the  place  of  the  horizontal 
cross  wire  in  telescopic  sights  of  other  models.  The  vertical  wire 
indicates  deflection,  and  the  intersection  of  the  wire  and  horizontal 
line  is  laid  on  the  object  sighted.  Lateral  motion  is  given  the  dia- 
phragm by  a  deflection  screw  on  the  right  side  of  the  telescope. 
The  movement  of  the  vertical  wire  is  a  little  more  than  2°  on  each 
side  of  the  zero  of  the  deflection  scale,  and  the  scale  itself  is 
graduated  to  0.05°  to  indicate  this  movement.  On  this  scale  the 
degree  marks  are  numbered,  the 'half  degrees  being  indicated  by  the 
number  50.  The  vertical  scale  reads  to  0°  3'  26",  equal  to  .001  of 
the  range.  It  is  intended  to  assist  in  estimating  distances,  errors  of 
range,  etc. 

The  telescope  is  properly  focused  when  the  plane  of  the  cross 
wires  is  in  the  position  of  distinct  vision  and  the  image  of  the  object 
is  in  the  same  plane  as  the  cross  wires.  To  accomplish  this  condition 
both  the  eyepiece  and  the  objective  are  given  the  necessary  motions 
within  the  telescope  tube. 

The  motion  of  the  eyepiece  is  given  by  screwing  or  unscrewing 
it  in  its  housing,  and  that  of  the  objective  by  a  focusing  screw  collar 
back  of  the  sunshade. 

In  sighting,  the  intersection  of  the  cross  wires  is  brought  to  bear 
on  the  image  of  the  object  sighted;  and  this  process  is  precisely  the 
same  as  bringing  the  intersection  of  the  cross  wires  on  to  a  material 
object  in  the  same  plane  as  the  cross  wires,  and,  provided  the  focusing 
is  correct  for  each  observer,  there  can  be  no  variation  in  the  sight- 
ing. 

The  elevation  arc,  the  center  of  which  is  on  the  horizontal  axis 
of  the  telescope,  is  graduated  from  —7°  to  +22°,  but  owing  to  the 
space  occupied  by  the  vernier  these  limits  for  practical  purposes  are  —7° 
and  +16°. 

The  vernier  reads  to  2'.  It  is  fastened  to  the  vernier  piece  on 
the  telescope  forward  of  the  deflection  screw  and  is  provided  with 


378  THE  SERVICE  OF  COAST  ARTILLERY 

two  set  screws,  one  at  each  end,  for  the  purpose  of  securing  it  to  this 
piece,  as  well  as  for  purposes  of  adjustment. 

The  rocking-worm  spindle  is  a  distinct  feature  of  this  sight;  and 
the  change  was  made  to  provide  for  a  constant  pressure  of  the  worm 
spindle  in  the  worm  rack,  and  to  prevent  uneven  wear  of  the 
latter. 

The  line  of  sight  at  zero  deflection  is  the  optical  axis  of  the  tele- 
scope. 

A  level  is  attached  to  the  left  side  of  the  telescope.  Its  axis  is 
parallel  to  that  of  the  sight  trunnions,  or  axis  of  revolution  of  the 
sight.  This  level  enables  the  sight  to  be  used  as  a  quadrant  in  its 
own  bracket. 

Open  sights  on  top  of  the  telescope  are  provided  to  enable  the 
gunner  to  quickly  bring  an  object  into  the  field  of  the  telescope. 

The  angle  of  elevation  is  given  by  turning  a  milled-head  microm- 
eter screw  which  actuates  a  worm  spindle;  and  the  latter  engaging 
in  the  worm  rack  cut  in  a  projection  on  the  right  side  of  the  telescope 
gives  the  desired  angular  motion  to  the  telescope  about  its  horizontal 
axis.  For  one  complete  turn  of  this  micrometer  screw  the  telescope 
is  elevated  or  depressed  1°. 

Any  backlash  between  the  worm  spindle  and  the  worm  rack  is 
overcome  by  means  of  a  spring  pressing  upward  against  the  bottom 
side  of  the  telescope. 

The  micrometer  screw  which  actuates  the  worm  spindle  is  gradu- 
ated to  minutes.  It  is  provided  on  top  with  two  small  screws  which 
secure  the  collar  on  which  the  graduations  are  made.  Unscrewing 
them,  the  collar  can  be  turned  and  the  vernier  and  micrometer  readings 
made  to  agree. 

To  obtain  a  correct  angle  of  elevation  it  is  essential  that  the  eleva- 
tion arc  should  be  truly  vertical  for  all  angles  of  elevation  of  the 
gun,  and  for  any  inclination  the  gun  trunnions  might  have  to  the 
horizontal.  This  is  accomplished  by  means  of  a  cross  level,  fastened 
to  the  under  side  of  the  frame,  parallel  to  the  horizontal  axis  of  the 
telescope,  and  perpendicular  to  the  axis  of  revolution  of  the  sight. 
The  cross  level  is  provided  with  two  openings,  one  on  the  top  and  one 
on  the  bottom,  to  permit  of  easy  observation  in  direct  and  reverse 
laying. 

Telescopic  Sight,  Model  of  1897,  differs  from  model  of  1896  Mi  in 
having  a  slightly  larger  field  of  view  (5°  12');  a  larger  objective  (1.2 
inches),  and  a  power  of  nine. 

The  glass  reticule  and  vertical  scale  are  omitted,  and  the  engraved 


INSTRUMENTS,  DEVICES  AND  CHARTS  379 

horizontal  line  is  replaced  by  a  horizontal  platinum  wire  of  .001  inch 
diameter. 

Deflection  is  given  by  moving  the  sliding  diaphragm  along  a* 
graduated  horn  deflection  scale  placed  below  the  diaphragm.  The 
movement  permitted  is  about  2°  15'  on  each  side  of  the  zero  of  the 
scale,  the  latter  being  graduated  to  indicate  the  movement.  The 
degree  marks  only  are  numbered,  and  the  value  of  the  smallest  division, 
3',  is  indicated  by  the  symbol  -^  directly  under  the  zero  hole  of  the 
scale.  The  vertical  crosswire  indicates  the  .amount  of  deflection. 

Telescopic  Sight,  Model  of  1898,  is  a  new  design,  similar  to  the  earlier 
models  described,  in  its  method  of  attachment  to  the  sight  bracket, 
but  differing  from  them  in  general  construction  and  in  the  more 
important  details.  • 

The  sight  consists  of  two  principal  parts,  the  trunnion  casting 
and  the  telescope,  which  is  pivoted  to  the  casting  at  its  forward  end. 

The  trunnion  casting  is  made  of  phosphor-bronze  on  account  of 
its  great  hardness,  elasticity,  and  the  resistance  to  corrosion.  This 
casting  comprises  the  trunnions,  the  leveling  lug,  the  bearing  for  the 
horizontal  axis  of  the  telescope,  and  the  elevation  arc  with  the  bearing 
for  the  elevating- worm  spindle. 

To  provide  for  interchangeability,  the  dimensions  of  the  trunnions 
and  leveling  lug  are  made  the  same  as  in  the  other  telescopic  sights. 

The  bearing  of  the  horizontal  axis  of  the  telescope  is  drilled 
through  the  trunnion  casting  near  the  'forward  trunnion.  The  eleva- 
tion arc  and  the  bearing  for  the  elevating-worm  spindle  constitute 
one  piece.  This  latter  bearing  is  practically  dustproof,  being  closed 
entirely  in  rear,  and  having  only  sufficient  opening  in  front  for  the  worm 
rack  to  engage. 

The  elevation  arc  is  graduated   as  in  the  other  sights. 

The  fundamental  line  of  all  the  telescopic  sights  is  the  axis  of 
revolution  defined  by  the  trunnions,  and  since  the  elevation  arc  and 
the  bearing  for  the  horizontal  axis  of  the  telescope  form,  as  they  do, 
a  part  of  the. casting  which  contains  the  axis  of  revolution,  it  follows 
that  such  a  construction  is  all  that  can  be  desired. 

The  telescope  is  attached  to  the  trunnion  casting  by  its  horizontal 
axis  and  the  worm  rack.  The  horizontal  axis,  or  pivot  of  the  telescope, 
projects  through  the  trunnion  casting.  Within  the  bearing  for  this 
pivot  is  an  annular  groove  which  contains  a  spiral  spring,  one  end  of 
which  bears  against  the  trunnion  casting  and  the  other  against  the 
telescope.  This  spring  serves  to  overcome  any  backlash  in  the  worm 
rack  when  the  telescope  is  moved  in  altitude,  and  being  placed  under 


380  THE  SERVICE  OF  COAST  ARTILLERY 

considerable  strain  in  fitting  it  in  its  groove,  the  pressure  it  exerts 
against  the  telescope  in  every  position  is  practically  uniform. 

The  worm  rack  on  the  left  side  of  the  telescope  projects  into  the 
opening  in  the  trunnion  casting  and  engages  with  the  elevating-worm 
spindle. 

The  telescope  can  be  run  out  and  disengaged  entirely  from  the 
worm  spindle  without  affecting  the  adjustment  of  the  telescope. 

The  micrometer  screw  on  the  elevating-worm  spindle  is  graduated 
to  1',  and  its  adjustments  are  made  as  in  the  other  sights. 

The  vernier  is  attached  to  a  vernier  piece  on  the  left  side  of  the 
telescope,  and  is  adjusted  by  means  of  two  screws  working  into  the 
vernier  piece,  one  at  each  end,  and  against  two  shoulder  pieces  bearing 
against  the  vernier.  This  adjustment  differs  from  that  in  the  other 
sights  in  that  a  given  turn  of  an  adjusting  screw  produces  an  opposite 
movement  in  the  vernier. 

The  vernier  reads  to  2'. 

The  telescopic  level  is  fastened  to  the  right  side  of  the  telescope. 

The  level  is  a  minute  one,  the  bubble  moving  .1  of  an  inch  for  1' 
of  elevation. 

For  giving  deflection,  a  set  of  platinum  cross  wires,  one  vertical 
and  one  horizontal,  and  two  scales,  one  inside  and  one  outside,  are 
provided.  The  vertical  cross  wire  is  attached  to  a  sliding  diaphragm 
actuated  by  the  deflection  screw  on  the  right'  side  of  the  telescope. 
In  giving  deflection,  this  vertical  wire  moves  along  the  interior  horn 
scale,  and  indicates  the  reading.  In  addition,  this  diaphragm  has  a 
pointer,  which  at  the  same  time  moves  along  the  outside  silver  scale, 
giving  the  reading  without  looking  into  the  telescope.  The  tele- 
scope is  cut  away  at  this  place  to  make  room  for  the  outside  scale,  and 
to  reveal  the  pointer.  In  order  that  the  pointer  should  give  a  correct 
reading,  the  screw  actuating  the  fixed  diaphragm  is  accurately  cut, 
and  the  backlash  is  overcome  by  two  spiral  springs  working  against  the 
sliding  diaphragm. 

The  horizontal  cross  wire  is  attached  to  a  fixed  diaphragm  placed 
behind  the  sliding  one.  For  the  purpose  of  adjustment,  this  dia- 
phragm can  be  given  a  slight  motion  in  a  vertical  direction  and  secured 
in  the  correct  position. 

The  interior  horn  scale  is  graduated  to  2°  30'  on  each  side  of  the 
zero.  The  smallest  division  is  3'.  This  scale  is  held  and  adjusted 
as  in  the  other  telescopic  sights;  on  the  scale  is  engraved  IU-FIRE— »L, 
indicating  the  direction  of  motion  for  the  vertical  cross  wire  in  order 
to  direct  the  gun  to  the  left  or  right  of  the  object  sighted. 


INSTRUMENTS,  DEVICES  AND  CHARTS  381 

The  cross  wires  and  the  fixed  and  sliding  diaphragms  are  exposed 
to  view  by  unscrewing  the  four  screws  holding  the  cap,  which  contains 
the  socket  for  the  eyepiece. 

The  outside  scale  is  graduated  to  degrees  and  half  degrees,  the 
3'  readings  being  obtained  from  the  micrometer-deflection  screw. 
The  inscription  R<—  FIRE— >L  is  also  engraved  on  this  scale. 

The  micrometer-deflection  screw  which  actuates  the  sliding  dia- 
phragm is  graduated  on  its  collar,  with  two  series  of  figures  from 
0  to  9  in  opposite  directions.  Each  division  equals  3',  and  a  complete 
turn  of  the  screw  moves  the  sliding  diaphragm  30'.  One  series  of  figures 
gives  the  correct  reading  when  the  deflection  movement  is  for  firing 
to  the  left  and  the  other  series  for  the  contrary  movement. 

L 

On  the  telescope  near  the  graduated  collar  is  engraved   J  ,  indi- 

R 

eating  the  direction  of  rotation  of  the  micrometer  deflection  screw 
for  firing  to  the  left  or  right  of  the  object  sighted. 

The  cross  level  is  attached  to  the  under  side  of  the  telescope  and 
is  provided  with  an  opening  at  the  top  for  direct  laying  and  one  at 
the  bottom  for  reverse  laying.  The  level  tube  fits  in  a  larger  tube 
cast  with  the  telescope,  and  for  the  purpose  of  adjustment  is  provided 
with  four  radial  set  screws  which  fit  in  a  flare  at  one  end  of  the  level 
tube  and  bear  against  the  outside  tubes. 

The  level  is  a  3'  one,  the  bubble  moving  a  tenth  of  an  inch  for  a 
change  of  inclination  of  3'. 

The  telescope  attached  to  this  sight  was  especially  designed  to 
give  a  large  field  of  veiw,  an  erect  image,  and  the  maximum  amount 
of  light  the  eye  will  receive  under  the  most  unfavorable  conditions. 

The  field  of  view  of  a  telescope  depends  on  its  power  and  the  field 
of  the  eyepiece.  Ordinarily  the  field  of  an  eyepiece  rarely  exceeds 
40°,  but  in  this  case,  besides  making  the  eyepiece  achromatic,  the 
field  was  increased  to  nearly  50°.  An  increase  of  this  amount  in  the 
field  of  the  eyepiece  is  always  accompanied  by  lack  of  perfect  definition 
at  the  margin  of  the  field.  By  dividing  the  field  of  the  eyepiece  by 
the  power  of  the  telescope,  its  field  of  view  is  obtained.  In  this  tele- 
scope the  field  of  the  eyepiece  is  48°,  and  the  power  is  8,  consequently 
the  field  of  the  telescope  is  6°. 

The  power  of  8  was  selected  as  sufficient  for  proper  magnification 
of  the  deflection  scale,  and  any  power  above  8  would  have  corre- 
spondingly diminished  the  field  of  view. 

The  erect  image  is  formed  by  the  insertion  of  a  Hastings-Brashear 
erecting  prism  between  the  eyepiece  and  the  objective.  The  opening 


382  THE  SERVICE  OF  COAST  ARTILLERY 

for  the  insertion  of  the  prism  and  its  frame  is  made  in  the  under  side 
of  the  telescope  tube. 

The  eye  receives  the  maximum  amount  of  light  through  a  tele- 
scope of  this  character,  when  the  diameter  of  the  pencil  of  light 
emerging  from  the  eyepiece  is  equal  to  that  of  the  pupil  of  the  eye. 
The  diameter  of  the  emerging  pencil  is  equal  to  the  diameter  of  the 
objective  divided  by  the  power  of  the  telescope.  To  fulfill  this  condition 
the  diameter  of  the  objective  is  made  1.25  inches;  the  diameter  of 
the  emerging  pencil  of  light  is  therefore  nearly  -J-  inch.  Except  at 
night,  when  the  pupil  of  the  eye  may  dilate  to  J-  inch,  the  telescope  is 
adapted  to  all  conditions  of  light. 

The  loss  of  light  in  the  telescope  is  due  to  absorption  in  the  lenses 
and  prism,  and  when  these  are  made  of  the  best  glass  and  the  sur- 
faces carefully  prepared,  the  loss  of  light  is  reduced  to  a  minimum. 

The  objective  is  focused  by  a  focusing  collar  back  of  the  sun- 
shade. 

The  eyepiece  is  focused  by  screwing  or  unscrewing  it  in  its  bearing, 
which  forms  part  of  the  cap  covering  the  deflection  scale  and  cross 
wires. 

The  sunshade  with  the  dew  cap  is  retained  in  place  by  a  small  set 
screw  which  permits  the  sunshade  to  be  pulled  in  or  out,  and  rotated 
about  the  telescope. 

The  telescope  tube  is  made  of  thick  brass,  so  that  it  may  be  handled 
without  danger  of  bending  or  the  sight  losing  its  adjustments. 

Use  of  the  Sight. — There  is  a  tendency,  among  those  making  a 
first  acquaintance  with  the  telescopic  sight,  to  think  it  a  very  compli- 
cated instrument,  having  little  in  common  with  the  ordinary  sights, 
and  that  to  learn  how  to  use  it  is  a  difficult  matter.  As  a  matter  of 
fact  it  is  simply  a  sight  in  the  form  of  a  telescope;  and  every  rule 
learned  about  elevation,  etc.,  is  precisely  the  same  as  with  the  ordinary 
sights,  only  of  easier  application,  the  operations  being  mechanical; 
besides  the  telescope  and  its  elevating  gear,  there  is  only  the  means  of 
attaching  it  to  the  gun,  which  a  little  information  will  make  quite 
clear. 

The  advantages  gained  by  the  use  of  the  telescopic  sight  are: 

Increased  accuracy  of  fire  due  to — 

a.  Power  of  vision. 

b.  Elimination  of  personal  error. 

(a)  Power  of  vision. — Objects,  indistinct  to  the  naked  eye,  in 
some  lights  almost  invisible,  can  be  seen  clearly,  and  accurately  aimed 
at,  even  at  the  extreme  range  of  effective  fire. 


INSTRUMENTS,  DEVICES  AND  CHARTS  383 

A  short-sighted  man  can  see  and  aim  just  as  well  as  a  man  with 
good  eyes. 

A  particular  part  of  the  object  can  be  aimed  at,  instead  of  an 
indistinct  whole,  and  no  part  of  the  object  is  obscured,  as  so  often 
happens  with  the  ordinary  front  sight. 

(6)  Elimination  of  personal  error. — A  -fine  cross  wire  has  to  be 
brought  mechanically  on  to  the  object — a  much  easier  thing  than 
aiming  exactly  with,  a  full  sight,  and  everyone  must  aim  the  same 
providing  the  focusing  is  correct. 

Before  using  a  sight,,  the  case  containing  it  should  be  slung  over 
the  gunner's  shoulder,  and  the  sight  should  not  be  removed  until 
the  gunner  has  reached  the  sighting  platform.  While  the  sight  is 
in  the  case,  the  cover  should  be  kept  fastened. 

In  removing  a  sight  from  its  case,  take  hold  of  the  strap  fastened 
to  the  frame  or  to  the  telescope. 

See  that  the  objective  is  screwed  home.  Neglect  of  this  precaution 
may  give  rise  to  a  large  error,  since  the  optical  center  of  the  objective 
may  not  coincide  with  the  axis  of  the  screw,  and  a  change  in  the  position 
of  the  optical  center  involves  at  once  a  change  in  the  line  of  sight. 

The  focusing  screw  collar  has  slightly  more  movement  than  is 
necessary  for  solar  focus,  and  the  telescope  is  first  focused  by  focusing 
the  eyepiece,  which  is  done  by  screwing  the  eyepiece  until  the  cross 
wires,  with  every  roughness  on  them,  are  distinctly  visible.  On  account 
of  the  coarseness  of  the  cross  wires,  this  is  not  a  very  sensitive  method 
of  focusing  the  eyepiece,  and  final  focusing  may  be  necessary  after  the 
objective  is  focused.  The  objective  is  focused  by  directing  the  telescope 
on  a  distant  object  and  turning  the  focusing  collar  until,  on  shifting  the 
eye  over  the  eyepiece,  the  intersection  of  the  cross  wires  remains  on 
the  same  point  of  the  object  (or,  in  other  words,  there  is  no  parallax). 
The  distant  object  selected  for  this  purpose  should  possess  sharp  out- 
lines. Telegraph  wires,  signposts,  or  buildings  are  excellent  for  the 
purpose.  The  general  landscape,  possessing,  as  it  does,  soft  outlines, 
should  not  be  used. 

When  the  objective  is  focused,  should  the  image  not  be  clearly 
defined,  then  the  eyepiece  is  not  correctly  focused,  and  it  must  be 
screwed  until  the  definition  is  satisfactory. 

An  objective  once  focused  is  correct  for  all  observers,  but  the 
eyepiece  requires  focusing  for  each  individual. 

Unless  disturbed,  an  objective  once  focused  will  remain  so  indefi- 
nitely. 


384  THE  SERVICE  OF  COAST  ARTILLERY 


The  Sight  as  used  in  Gun  Laying 

The  sight  is  now  ready  for  use  in  gun  laying. 

To  set  the  sight  for  deflection,  take  hold  of  it  with  the  left  hand, 
and,  looking  into  the  telescope,  move  the  deflection  screw  with  the 
thumb  and  forefinger  of  the  right  hand  until  the  required  deflection 
is  obtained. 

Right  deflection  corrects  for  deviation  in  firing  where  the  shots 
fall  to  the  left  of  the  target,  and  left  deflection  the  contrary. 

To  avoid  confusion,  the  model  of  1897  sight  has  engraved  on  the 
body  of  the  telescope,  and  beside  the  deflection  screw  controlling 
the  sliding  diaphragm,  the  expression  "Drift  correction/'  and  an 
arrowhead  to  indicate  the  direction  of  motion  to  make  the  correction. 

The  inscription,  "Drift  correction/'  was  placed  on  the  sight  as  a 
guide  in  the  movement  of  the  cross  wires  to  correct  for  various  deviat- 
ing causes.  It  must  not  be  understood  that  the  sight  corrects  for 
drift  only. 

In  the  model  of  1898  sight  and  model  of  1898  M  sight,  the  inside  and 
outside  deflection  scales,  and  the  telescope  near  the  micrometer,  deflec- 
tion screws  have  engraved  on  them  the  direction  of  the  movement  of 
the  vertical  cross  wire  in  order  to  direct  the  gun  to  the  left  or  right  of 
the  object  sighted. 

Should  the  shot  fall  to  the  right  of  the  target,  to  make  the  correction 
the  vertical  cross  wire  is  moved  the  proper  amount  in  the  direction 
indicated  by  the  arrowhead  pointing  toward  the  letter  L.  Looking 
into  the  telescope,  this  motion  is  to  the  right. 

Should  the  shot  fall  to  the  left  of  the  target,  the  movement  of  the 
vertical  cross  wire  is  in  the  contrary  direction  and  as  indicated  by  the 
arrowhead  pointing  toward  the  letter  R. 

It  is  readily  seen  that  the  sliding  diaphragm  moves  to  the  right 
to  correct  for  drift,  or  for  a  similar  deviating  cause. 

These  sights  correct  for  drift,  wind,  and  speed  of  target. 

To  set  the  sight  for  elevation,  turn  the  micrometer  screw  control- 
ling the  elevating-worm  spindle  until  the  required  elevation  is  obtained. 

Since  the  worm  rack  is  not  apt  to  wear  uniformly,  it  is  preferable 
to  depend  entirely  on  the  vernier  for  the  2'  readings,  and  to  use  the 
graduations  on  the  collar  of  the  elevating  screw  for  the  odd  minute. 

Let  the  angle  of  elevation  required  be  2°  35'.  To  set  the  sight, 
turn  the  elevating  screw  until  the  arrow  on  the  vernier  points  to 
2°  30',  now  turn  the  same  screw  until  the  second  graduation  from 


INSTRUMENTS,   DEVICES  AND  CHARTS  3S5 

the  arrow  on  the  vernier  is  brought  into  line  with  the  graduation 
on  the  elevation  arc  just  in  front  of  it.  The  reading  is  now  2°  34', 
and  to  obtain  the  required  elevation,  turn  the  micrometer  screw 
through  the  extra  minute  indicated  on  the  graduated  collar. 

The  sight  is  now  ready  to  be  placed  in  its  bracket  on  the  gun 
trunnion,  and  in  seating  it  be  very  careful  to  bring  the  leveling  lug 
to  bear  gently  against  the  leveling  screw.  If  this  one  precaution  is 
heeded,  the  sight  will  ordinarily  never  lose  its  adjustments. 

The  sight  is  leveled  by  turning  the  leveling  screw  until  the  bubble 
in  the  cross  level  comes  to  its -center. 

Looking  along  the  telescope,  or  through  the  open  sights,  or  along 
the  axis  of  the  sight  trunnions,  the  gun  carriage  is  quickly  traversed 
until  the  target  is  brought  into  the  field  of  view. 

If  the  target  appears  below  the  intersection  of  the  cross  wires, 
depression  is  required;  if  above  the  intersection  of  the  cross  wires,  the 
gun  must  be  elevated.  If  the  target  is  seen  to  the  right  of  the  cross 
wires,  the  gun  carriage  must  be  traversed  "muzzle  right";  if  to  the 
left,  "muzzle  left." 

With  barbette  carriages,  owing  to  the  slight  preponderance  of  the 
breech  of  the  gun,  it  is  preferable  in  order  to  overcome  any  backlash 
in  the  elevating  gearing  that  depression  should  be  the  last  opera- 
tion. 

The  intersection  of  the  cross  wires  having  been  brought  on  that 
part  of  the  target  aimed  at,  look  at  the  cross  level,  and  if  the  bubble 
is  still  in  the  center,  the  gun  is  correctly  laid.  If  the  bubble  is  not 
in  the  center  of  the  cross  level,  the  gun  is  not  correctly  laid,  and  the 
sight  must  be  releveled  and  the  operation  of  laying  repeated  until 
the  condition  obtains  that  when  the  sight  is  directed  on  the  target  the 
bubble  shall  be  in  the  center  of  the  cross  level.  In  sighting  a  gun 
mounted  on  a  seacoast  carriage,  the  axis  of  the  gun  trunnions  being 
horizontal,  the  bubble  will  remain  in  the  center  of  the  cross  level  during 
the  entire  operation  of  laying.  The  last  act  of  the  gunner  before  firing, 
.should  be  to  see  whether  or  not  the  bubble  is  in  the  center  of  the  cross 
level. 

The  telescopic  level  enables  the  gunner  to  use  the  quadrant  angle 
of  elevation,  in  which  case  the  sight  is  first  set  for  deflection  only, 
and  the  gun  is  aligned  with  the  telescope  at  a  convenient  angle  of 
-elevation.  The  gun  having  been  aligned  on  the  target,  the  sight  is 
set  for  the  required  quadrant  angle  of  elevation,  and  the  gun  elevated 
or  depressed  until  the  bubble  in  the  telescopic  level  comes  to  its  center. 

Using  the  sight  as  a  quadrant  has  the  advantage  of  eliminating 


386  THE  SERVICE  OF  COAST  ARTILLERY 

any  error  due  to  refraction,  which  is  likely  to  be  present  where  the  site 
of  the  gun  is  at  an  elevation  above  the  target. 

A  correction  must  be  applied  to  the  angle  of  elevation  to  obtain 
the  quadrant  angle,  depending  on  the  height  of  the  gun  site  above  the 
target.  Both  angles  are  alike  when  the  gun  and  target  are  on  the  same 
level. 

For  reverse  laying,  the  sight  is  reversed  in  its  bracket  and  leveled , 
the  cross  level  being  exposed  on  its  under  side  to  render  the  bubble 
visible. 

When  the  sight  is  placed  in  the  bracket  on  the  sight  standard  of 
a  disappearing  or  barbette  carriage,  it  is  leveled  as  before;  but  in  this 
position  it  can  only  be  used  for  giving  direction,  and  accordingly  is 
set  for  deflection  only,  the  elevation  of  the  gun  being  given  by  the 
elevation  arc. 

Tests  and  Adjustments  of  the  Sights. — The  principles  involved 
in  the  construction  of  telescopic  sights  require  : 

1.  That  the  line  of  sight  at  zero  deflection  and  elevation  and  tlie 
axis  of  the  telescopic  level  should  be  parallel  to  the  axis  of  revolu- 
tion. 

2.  That  the  axis  of  the  cross  level  should  be  perpendicular  to  the 
elevation  arc  and  to  the  axis  of  revolution. 

3.  That  the  sight  trunnions  should  be  of  equal  diameter. 

4.  That   the   sliding   diaphragm   carrying   the    cross   wires   should 
move  in  setting  the  sight  for  deflection  parallel  to  the  axis  of  the  cross 
level. 

In  addition  to  the  above,  the  following  tests  are  prescribed  for 
each  sight: 

A  test  of  the  elevation  arc  and  deflection  scale  for  accuracy. 

A  test  of  each  level  for  sensitiveness. 

A  test  of  the  telescope  for  definition,  field  of  view,  and  power. 

Before  making  any  tests  of  a  sight,  see  that  the  objective  and  the 
eyepiece  lenses  are  clean,  and  that  the  objective  is  screwed  home. 

1.  Test  for  parallelism  of  the  line  of  sight  at  zero  deflection  and 
elevation  to  the  axis  of  the  telescopic  level  and  to  the  axis  of  revolution 
of  the  sight: 

To  make  this  test,  it  is  desirable  to  have  a  stand  on  which  to  place 
the  sight,  a  striding  level  to  level  the  trunnions,  and  an  engineer's 
Y  level. 

To  make  the  examination,  place  the  trunnions  on  the  stand,  level 
them  with  the  striding  level,  make  the  cross  level  read  zero,  and  then, 
by  means  of  the  elevation  micrometer  screw,  make  the  telescopic 


INSTRUMENTS,  DEVICES  AND  CHARTS  387 

level  read  zero.  This  will  bring  the  axis  of  the  level  and  the  axis  of 
the  revolution  into  parallel  planes,  which  are  horizontal. 

Then  see  if  the  vernier  reads  zero  on  the  arc.  If  it  does  not,  either 
make  it  do  so  by  means  of  the  proper  adjusting  screws  or  note  the 
error. 

The  vernier  is  adjusted  by  means  of  two  set  screws,  one  at  either 
end  of  the  vernier,  so  arranged  that,  by  unscrewing  one  of  the  screws 
and  screwing  up  the  other,  the  vernier  can  be  adjusted  in  the  required 
direction. 

To  make  the  zero  of  the  micrometer  divisions  on  the  milled  head 
screw  for  elevating  agree  with  the  zero  of  the  vernier,  loosen  the  two 
small  screws  on  top  of  the  brass  head,  then  turn  the  collar  carrying  the 
divisions  into  the  proper  position,  and  tighten  the  two  small  screws. 

Next,  focus  the  telescope  of  the  sight  on  a  distant  object,  set  up 
the  engineer's  Y  level,  focus  it  on  a  distant  object,  adjust  it  carefully 
to  indicate  a  level  line,  and  make  sure  that  there  is  no  parallax  in  the 
eyepiece  of  either  telescope.  That  being  done,  and  the  telescope  of 
the  level  being  collimated  on  the  telescope  of  the  sight,  with  the  object 
glasses  2  or  3  inches  apart,  look  into  the  telescope  of  the  level  and  see 
if  its  horizontal  wire  coincides  with  the  horizontal  pointer  or  horizontal 
cross  wire  in  the  sight.  If  there  is  any  error,  note  its  amount. 

In  the  model  of  1896  Mi  sight,  this  error  can  be  corrected  by  adjust- 
ing horizontally  the  line  on  the  glass  reticule,  the  latter  being  adjustable 
after  loosening  the  two  screws  which  secure  it  and  its  frame  in  a  vertically 
adjustable  frame  which  in  turn  is  held  by  two  screws. 

To  remove  the  eyepiece  cap  so  as  to  render  the  reticule  and  frames 
accessible  first  remove  the  four  screws  at  the  right  of  the  eyepiece 
which  secure  the  split  housing  for  the  deflection  knob,  when  two  other 
screws  will  be  exposed  which  must  also  be  removed  in  addition  to  the 
two  screws  at  the  left  of  the  eyepiece,  when  the  cap  can  be  removed 
by  drawing  it  directly  toward  the  operator. 

In  the  model  of  1897  sight  this  error  can  be  corrected  by  the  adjust- 
ing screws  of  the  erecting  prism,  tilting  the  line  of  collimation  suffi- 
ciently to  compensate  for  the  error;  these  sights  are,  however,  being 
fitted  as  rapidly  as  possible  with  a  vertically  adjustable  diaphragm, 
to  which  the  horizontal  wire  is  attached  similar  to  the  model  of  1898 
sight,  and  when  so  equipped  the  erecting  prism  should  not  be  dis- 
turbed. This  diaphragm  has  a  small  screw  and  opposing  spring,  by 
means  of  which,  after  loosening  the  three  screws  which  hold  it  in  place, 
the  diaphragm  can  be  adjusted  very  minutely  and  clamped  securely 
as  before. 


388  THE  SERVICE  OF  COAST  ARTILLERY 

In  the  model  of  1898  and  1898  M  sights,  the  error  is  corrected  by 
moving  in  the  direction  required  the  diaphragm  carrying  the  hori- 
zontal wire.  These  sights  are  being  equipped  with  the  fine  adjust- 
ment above  described. 

This  test  shows  whether  or  not  the  line  of  collimation  of  the  tele- 
scope is  parallel  to  the  axis  of  revolution  in  the  horizontal  plane.  It 
yet  remains  to  be  seen  whether  it  is  parallel  in  the  vertical  plane; 
For  that  purpose  revolve  the  sight  on  its  trunnions  through  an  angle 
of  90°,  so  as  to  bring  the  cross  level  vertical,  and  then  having  again 
brought  the  engineer's  level  into  position,  look  through  it  into  the 
telescope  of  the  gun  sight,  and  notice  whether  or  not  the  horizontal 
wire  of  the  level  cuts  the  extreme  tip  of  the  horizontal  pointer  or  the 
intersection  of  the  cross  wires  when  the  deflection  scale  reads  zero. 
If  they  do,  all  is  well;  if  not,  by  means  of  the  deflection  screw,  move 
the  horizontal  pointer  or  cross  wires  until  its  extreme  tip  or  their 
intersection  touches  exactly  the  horizontal  wire  of  the  engineer's  level. 
The  eye  end  is  closed  by  a  cap,  held  by  four  screws  which  must  be 
unscrewed.  When  this  is  done,  the  deflection  scale  will  be  exposed, 
and  it  will  be  seen  that  it  is  held  in  place  by  two  small  screws.  Loosen 
these  screws,  shift  the  scale  so  as  to  make  its  zero  coincide  accurately 
with  the  pointer  or  cross  wire;  tighten  the  screws  so  as  to  clamp  the 
scale  firmly,  and  replace  the  cap  which  carries  ,the  eyepiece.  If  these 
operations  are  properly  performed,  the  deflection  scale  will  be  brought 
into  perfect  adjustment,  but  it  should  be  again  tested  with  the  engineer's 
level  to  make  sure  that  such  is  the  case. 

To  determine  whether  the  axis  of  the  telescopic  level  is  parallel  to 
the  axis  of  the  sight  trunnions  or  axis  of  revolution,  revolve  the  sight 
through  a  small  angle  about  its  trunnions,  the  level  and  trunnions 
both  being  horizontal;  if  the  parallelism  is  present,  the  bubble  will 
remain  in  the  center  of  the  level;  if  not,  the  instrument  maker  only 
can  correct  it. 

2.  Test  to  determine  whether  the  axis  of  the  cross  level  is  perpen- 
dicular to  the  elevation  arc,  and  to  the  axis  of  revolution  of  the  sight: 

Place  the  sight  in  its  bracket  with  the  axis  of  the  V  bearings 
approximately  horizontal,  and  level  the  cross  level.  Suspend*  a  plumb 
line  of  sufficient  length  to  subtend  the  elevation  arc  about  15  yards 
from  the  sight,  and  move  the  sight  until  the  intersection  of  the  cross 
wires  bears  accurately  on  the  top  of  the  line.  Now  move  the  tele- 
scope in  altitude  until  it  is  sighted  on  the  bottom  of  the  line.  If  the 
intersection  of  the  cross  wires  bears  accurately  on  the  bottom  of  the 
line,  the  axis  on  the  cross  level  is  in  a  plane  perpendicular  to  the  eleva- 


INSTRUMENTS,  DEVICES  AND  CHARTS  389 

tion  arc.  If  not,  adjust  the  cross  level  in  the  model  of  1896  Mi  and 
model  of  1897  sights,  as  follows: 

Unscrew,  by  half  a  turn  at  a  time,  each  of  the  two  screws  of  the 
level,  just  sufficiently  to  admit  of  a  piece  of  paper  being  inserted  under- 
neath the  proper  screw  end  of  the  level. 

The  paper  must  be  rectangular,  having  a  piece  cut  out  of  it  in 
order  that  it  may  envelop  the  screw  on  three  sides.  One  thickness 
of  foolscap  paper  raises  the  level  about  1'. 

If  the  pointer  was  to  the  right,  raise  the  level  on  the  left  side;  if 
to  the  left,  on  the  right  side,  by  means  of  the  piece  of  paper  put  under- 
neath. 

Finally,  screw  the  screws  home  equally,  and  with  moderate  force. 
Re  apply  the  test,  and  if  found  correct  make  a  scratch  across  the  heads 
of  the  screws  to  the  metal  of  the  sight.  If  not  correct,  the  operation 
must  be  repeated. 

To  make  the  adjustment  in  the  model  of  1898  sight,  unscrew  the 
screw  cap  on  the  right  end  of  the  cross-level  casting.  This  will  expose 
the  level  tube  with  four  adjusting  set  screws.  The  position  of  these 
screws  will  at  once  suggest  the  correct  ones  to  adjust  to  make  the 
correction. 

To  complete  the  test,  the  experiment  must  be  repeated  with  the 
axis  of  the  V  bearings  at  the  maximum  elevation  the  experiment 
will  permit. 

If,  then,  the  intersection  of  the  cross  wires  follows  the  plumb  line 
the  axis  of  the  cross  level  is  truly  at  right  angles  to  the  axis  of  revolu- 
tion and  to  the  elevation  arc.  If  not,  then  in  the  model  of  1896  Mi 
and  model  of  1897  sights  the  adjustment  must  be  made  by  unscrewing 
the  two  screws  holding  the  cross  level  and  forcing  sidewise  one  end  of 
the  level  sufficient  to  correct  for  the  error,  and  then  tightening  the 
screws.  If  there  is  not  sufficient  play  in  the  screw  holes  to  make  the 
correction,  the  sight  should  be  returned  to  the  maker.  In  the  model  of 
1898  the  correction  is  made  by  adjusting  the  set  screws  of  the  level  tube 
so  as  to  move  it  sidewise. 

Repeat  the  preceding  experiment  for  test  of  the  adjustments 
made. 

3.  Test  for  equality  in  the  diameters  of  the  sight  trunnions: 

Use  a  Brown  &  Sharpe  micrometer,  measuring  each  diameter 
with  the  utmost  care.  With  skill  the  measurement  can  be  made 
to  one  five-thousandth  (0.0002)  part  of  an  inch,  and  if  the  trunnions 
differ  by  more  than  that  they  should  be  returned  to  the  maker  for 
correction. 


390  THE  SERVICE  OF  COAST  ARTILLERY 

The  striding  level  will  answer  the  purpose  even  better  than  the 
micrometer  calipers. 

4.  Test   for   the   horizontal   movement   of   the   sliding   diaphragm 
when  the  sight  is  leveled: 

This  test  can  be  made  in  conjunction  with  the  test  for  the  par- 
allelism of  the  axis  of  revolution  and  the  line  of  sight  at  zero  deflection 
and  elevation.  The  telescope  of  tho  sight  being  adjusted  and  its  line  of 
sight  at  zero  deflection  and  elevation  horizontal,  and  the  telescope 
of  the  Y  level  being  horizontal  and  collimated  on  that  of  the  sight, 
when  the  horizontal  pointer  or  cross  wires  should  coincide  with  the 
horizontal  wire  of  the  Y  level.  Move  the  sliding  diaphragm  carrying 
the  pointers  or  cross  wires,  when,  if  the  sight  is  in  adjustment,  the 
coincidence  should  remain  undisturbed  during  the  deflection  of  the 
pointers  or  cross  wires.  If  the  horizontal  pointer  or  cross  wire  rises 
above  or  falls  below  the  horizontal  wire  in  the  level,  the  sight  is  not  in 
adjustment,  and  the  defect  can  only  be  remedied  by  the  maker. 

5.  To  test  the  vertical  arc,  the  most  convenient  plan  will  be  to 
fasten  the  instrument  on  a    stand  with  the  vertical  arc  lying  hori- 
zontally, and  point  the  telescope  on  some  distant  object,  in  such  a 
direction  that  the  vernier  is  near  one  extremity  of  the  arc.     Read 
the  arc,  and  then  point  on  another  distant  object  so  situated  as  to 
bring  the  vernier  nearly  to  the  other  extremity  of  the  arc,  and '  read 
the  arc  again.     The  difference  of  these  two  readings  will  be  the  angular 
distance  between  the  objects.     Then  remove  the  gun  sight,   set   an 
ordinary  theodolite  in  its  place,  and  measure  the  angle  between  the 
same  objects  with  it.     If  all  is  right,  the    arc   as  measured  by  the 
theodolite  should  be  the  same  as  that  indicated  by  the  gun  sight.     In 
making  this  test  care  must  be  taken  to  place  the  center  of  the  theodolite 
as  nearly  as  possible  in  the  position  which  was  occupied  by  the  horizontal 
axis  of  the  telescope  of  the  gun  sight.     The  vertical  limb  of  the  transit 
may  be  used  for  the  same  purpose  when  there  are  facilities  for  doing  so. 
If  it  is  thought  best,  collimated  telescopes  can  be  used    instead  of 
distant  objects. 

6.  To  determine  the  value  of  the  horizontal  scale  of  the  gun  sight, 
set  up  a  theodolite  in  such  a  position  that  its  telescope  collimates  on 
the  telescope  of  the  gun  sight,  and  measure  on  the  limb  of  the  theodolite 
any  convenient  number  of  the  divisions  of  the  horizontal  scale  of  the 
gun  sight.     Dividing  the  arc  thus  measured  by  the  number  of  divisions 
will  give  the  value  of  each  single   division.     When   using  collimated 
telescopes,  always  take  the  precaution  to  focus  each  one  on  a  distant 
object  before  collimating. 


INSTRUMENTS,  DEVICES  AND   CHARTS  391 

7.  Examine   the   telescope   by   measuring   its   aperture   in   inches, 
its   focal   distance   in   inches,   and   its   magnifying   power.     The   best 
method  of  determining  the  magnifying  power  is  by  means  of  a  double- 
image  dynameter,  but  it  is  not  necessary  to  employ  such  an  elaborate 
apparatus  in  the  present  case.     It  will  suffice  to  take  the  clear  aperture 
of  the  objective  between  the  points  of  a  pair  of  dividers  and  prick  it 
down  on  a  piece  of  paper.     Then,  with  the  same  pair  of  dividers  and 
a  magnifying  glass,  take  the  diameter  of  the  pencil  of  light  emerging 
from  the  eyepiece,  and  find  how  many  times  that  is  contained  in  the 
clear  aperture  of  the  objective  by  using  the  last  opening  of  the  dividers 
to  step  the  distance  between  dots  laid  down  when  the  objective  was 
measured.     The  result  will  be  the  magnifying  power.     Finally,  examine 
the  definition  of  the  telescope,  and  note  whether  or  not  it  is  satisfactory. 

An  accurate  determination  of  the  focal  distance  of  the  telescope 
is  not  necessary.  The  telescope  being  focused  on  a  distant  object, 
it  will  suffice  to  measure  the  distance  from  the  front  of  its  objective 
to  the  pointers,  and  then  deduct  two-thirds  of  the  thickness  of  the  object 
glass. 

For  determining  the  field  of  view  the  following  method  is  suggested : 
When  the  telescope  of  the  sight  and  transit  instrument  are  colli- 
mated  on  each  other,  the  diameter  of  the  field  of  view  can  be  deter- 
mined by  pointing  the  transit  first  on  one  end  of  the  diameter  and 
then  on  the  other,  reading  the  angles  and  taking  the  difference. 

8.  A  test  to  determine  the  sensitiveness  of  the  telescopic  level: 
Bring  the  bubble  to  one  end  of  its  run  by  means  of  the  elevation 
micrometer  screw  on  the  telescope  and  note  the  reading  on  the  arc 
of  elevation.     Then,  by  means  of  the  elevating  screw,  bring  the  bubble 
to  the  other  end  of  its  run,  and  again  read  the  arc  of  elevation.     The 
difference  of  these  two  readings  is  the  amount  of  arc  corresponding 
to  the  distance  traversed    by  the  bubble  in  passing  from  one  end  of  its 
run  to  the  other.     This  should  be  at  the  rate  of  not  less  than  1  inch  for 
10'  of  elevation.     There  seems  to  be  no  convenient  way  of  testing  the 
sensitiveness  of  the  horizontal  level,  except  by  taking  it  off,  fastening 
it  on  the  telescope,  and  then  testing  it  in  the  same  way  as  the  telescopic 
level. 

The  preceding  tests  and  adjustments,  on  which  the  efficiency  of 
the  sights  depends,  are  carefully  made  during  manufacture,  and  unless 
a  sight  is  tampered  with,  or  subjected  to  rough  treatment,  it  is  most 
unlikely  to  ever  lose  its  adjustments.  In  manufacture  the  adjustments 
are  all  made  with  a  limiting  error  of  1'. 

In   service   it   is   desirable   that   the   sights   should   frequently   be 


392  THE  SERVICE  OF  COAST  ARTILLERY 

tested,  and  where  there  are  facilities  the  methods  laid  down  should 
be  followed. 

The  adjustments  must  not,  however,  be  made  except  by  an  officer 
authorized  to  do  so  by  the  Chief  of  Ordnance,  and  if  a  sight  is  found 
by  trial  to  be  out  of  adjustment  the  fact  should  be  reported  to 
proper  authority. 

At  a  fortification  where  the  facilities  are  few  for  making  the  pre- 
ceding tests,  the  following  methods  are  outlined  for  the  guidance  of 
the  officer  conducting  them: 

Tfre  test  for  the  equality  of  the  sight  trunnions,  the  accuracy  of 
the  elevation  arc  and  deflection  scale,  the  sensitiveness  of  the  levels, 
and  the  horizontal  motion  of  the  sliding  diaphragm  can  be  dispensed 
with,  since  the  sights  before  issue  to  the  service  have  been  tested  for 
these  requirements,  and  from  the  construction  of  the  sight,  it  is  obvious 
that  these  requirements  can  always  be  obtained. 

A  bracket  mounted  accurately  on  a  horizontal  gun  trunnion  will 
.answer  all  the  purposes  of  an  efficient  support  for  the  sight  during 
these  tests. 

1.  Test  for  the  parallelism  between  the  line  of  sight  at  zero  deflec- 
tion and  elevation,  and  the  axis  of  revolution: 

Test  each  sight  independently  by  setting  it  at  zero  deflection  and 
elevation,  and  laying  it  on  a  mark  about  3,000  yards  distant,  and 
revolving  the  sight  about  its  axis  of  revolution.  If  the  line  of  sight 
is  parallel  to  the  axis  of  revolution,  the  tip  of  the  pointer  or  the  inter- 
section of  the  cross  wires  will  remain  exactly  on  the  same  distant 
mark.  If  not,  deflect  the  sliding  diaphragm  and  elevate  or  depress  the 
telescope  until  the  tip  of  the  pointer,  or  the  intersection  of  the  cross 
wires,  remains  exactly  on  the  distant  mark.  Note  the  errors  in  eleva- 
tion and  deflection.  If  the  error  in  elevation  or  deflection  exceeds  1' 
the  sight  must  be  readjusted.  Select  that  sight  which  has  the  minimum 
errors  as  the  standard  sight. 

2.  Test  for  parallelism  between  the  axis    of    the  telescopic  level 
and  the  axis  of  revolution  of  the  sight: 

With  all  the  sights  set  at  the  true  line  of  sight  for  zero  deflection 
and  elevation,  elevate  or  depress  the  gun  until  the  telescopic  level 
reads  zero.  Revolve  the  sight  about  its  axis  of  revolution  through 
an  angle  of  about  5°.  If  the  axis  of  the  telescopic  level  is  parallel 
to  the  axis  of  revolution,  the  bubble  should  not  leave  the  center  of 
the  level. 

3.  Test  for  the  cross  level  being  at  right  angles   to   the  axis  of 
revolution  of  the  sight: 


INSTRUMENTS,  DEVICES  AND   CHARTS  393 

Level  the  cross  level  of  each  sight.  Elevate  the  gun  through  an 
angle  about  20°,  when  the  bubble  should  remain  stationary  in  the 
center  of  the  cross  level. 

4.  Test  for  the  cross  level  being  at  right  angles  to  the  vertical  arc: 

Lay  on  a  distant  mark  with  the  sight  set  at  zero  deflection  and 
elevation.  Elevate  the  gun  through  an  angle  of  about  15°.  Now 
depress  the  telescope  until  the  intersection  of  the  cross  wires  cuts  the 
point  aimed  at.  If  it  does  not  do  so  the  level  is  not  at  right  angles  to 
the  arc,  and  the  arc  is  not  vertical. 

Select  the  sights  that  have  fulfilled  the  preceding  tests  satis- 
factorily and  set  each  one  at  10°  elevation  and  zero  deflection,  and 
lay  each  one  carefully  on  a  distant  mark. 

The  sights  should  be  interchangeable  to  within  1',  and  this  test 
will  verify  all  the  preceding  tests  except  2.  If  the  sights  show  a 
disagreement  in  elevation  which  cannot  be  accounted  for  in  the  pre- 
ceding tests,  then  set  each  sight  at  the  zero  elevation,  and  if  the 
disagreement  still  holds,  it  is  due  to  the  trunnions  not  being  of  the 
same  diameter  and  the  trunnions  must  have  been  injured. 

After  a  sight  has  been  in  use  for  some  time  the  micrometer  of 
the  elevating  wTorm  may  be  found  not  to  agree  with  the  vernier.  This 
is  due  to  a  slight  wear  of  the  worm  rack,  and  when  the  vernier  and 
micrometer  are  made  to  agree  at  zero,  it  will  sometimes  be  found 
that,  owing  to  uneven  wearing  of  the  rack,  they  cannot  be  made  to 
agree  at  other  angles  of  elevation.  When  the  difference  is  considerable 
the  sight  should  'be  provided  with  a  new  rack. 


THE    GUNNER'S    QUADRANT 

This  instrument  (Fig.  60)  is  used  on  all  kinds  of  guns  and  mortars; 
either  to  give  the  elevation  directly  or  to  verify  the  angles  obtained  by 
ordinary  sights.  On  the  12-inch  mortars  two  seats  for  the  feet  of  the 
quadrant  are  squared  off  on  the  upper  side  of  the  piece  in  rear  of  the 
trunnions;  with  other  pieces,  the  quadrant  should  be  applied  to 
surfaces  perpendicular  or  parallel  to  the  axis  of  the  bore.  There  are 
three  models  in  service — 1892,  1897,  and  1898. 

The  quadrant  is  composed  of  two  main  parts — the  body,  carrying 
the  graduated  arc,  and  the  movable  arm,  carrying  the  index  and 
the  level.  The  movable  arm  also  carries  a  graduation  in  minutes  from 
0  to  60,  and  the  level,  which  is  capable  of  a  longitudinal  movement 
along  the  arm,  carries  a  second  index  for  reading  this  scale. 


394 


THE  SERVICE  OF  COAST  ARTILLERY 


Degrees  are  read  upon  the  graduated  arm  of  the  body,  minutes 
by  the  sliding  level,  and  scale  on  the  movable  arm. 

The  graduated  arc  is  provided  on  the  inside  with  a  toothed  circular 
rack,  each  tooth  of  which  corresponds  to  a  degree  mark.  The  mov- 
able arm  is  hollow  and  holds  a  spindle  which  carries  on  its  end  a  small 
toothed  sector.  A  spiral  spring  contained  inside  the  hollow  arm 
constantly  urges  the  spindle  and  sector  outward,  thereby  engaging  the 
teeth  of  the  sector  with  those  of  the  graduated  arc  and  holding  the  arm 
in  any  position  it  may  be  placed.  To  move  the  arm  it  is  necessary 


ARC".  (TEETH  ONE 
DEGREE  EACH)-  • 


FOOT  ''••'/?,  VERNIER, 
BEARINGS    CLAMP  SCREW 


VERNIER 


FIG.  60. — Gunner's  Quadrant. 

to  press  back  the  sector  against  the  action  of  the  spiral  spring  until 
its  teeth  clear  those  of  the  graduated  arc ;  the  arm  may  now  be  moved  to 
a  new  position,  and  when  the  pressure  is  removed  from  the  sector 
its  teeth  will  again  engage  with  those  of  the  graduated  arc. 

The  principle  by  which  the  scale  of  the  movable  arm  is  constructed 
to  read  to  minutes  is  as  follows: 

The  movable  arm  is  a  portion  of  the  arc  of  a  circle. 

The  level  is  a  chord  of  this  circle,  and  the  angle  between  any  two 
of  its  positions  will,  therefore,  be  that  subtended  by  the  arc  over 
which  the  index  moves. 


INSTRUMENTS,  DEVICES  AND  CHARTS  395 

To  Use  the  Quadrant. — It  should  be  remembered  that  a  correction 
must  be  made  to  the  angle  of  elevation  used  with  the  sight  to  obtain 
the  quadrant  angle  of  elevation,  and  that  this  correction  depends  on 
the  difference  in  height  above  sea  level  of  the  axis  of  the  trunnions 
and  the  target. 

QE  =SE+the  angular  elevation  of  the  target, 
or  when  target  is  below  the  level  of  the  gun,  as  is  the  usual  case: 
QE=SE—ihe  angular  depression  of  the  target. 

For  Angles  of  Elevation. — Set  the  quadrant  at  the  required  quadrant 
elevation  by  placing  the  index  mark  of  the  sector  of  the  movable 
arm  opposite  the  required  degree  mark  on  the  graduated  arc  of  the 
body,  and  by  sliding  the  level  along  the  arm  until  its  index  is  opposite 
the  required  minute  division  of  the  scale  of  the  movable  arm.  All 
elevations  below  45°  (both  degrees  and  minutes)  are  read  from  the 
scales  on  one  side  of  the  quadrant,  and  those  above  45°  from  the  scales 
on  the  other  side  of  the  quadrant. 

Place  the  quadrant  on  its  seats  or  on  surfaces  parallel  or  perpen- 
dicular to  the  axis  of  the  bore,  always  being  careful  to  keep  the  side 
of  the  graduated  arc  in  use  to  the  left,  looking  in  the  direction  of  the 
target,  and  keep  the  arrow  showing  the  line  of  fire  pointing  in  the 
direction  of  the  target.  Elevate  the  piece  until  the  bubble  of  the  level 
comes  to  rest  at  the  center.  This  will  be  the  elevation  required. 

For  Angles  of  Depression. — Proceed  as  above,  except  that  the 
side  of  the  graduated  arc  in  use  should  be  kept  to  the  right,  looking  in 
the  direction  of  the  target,  and  the  arrow  showing  "direction  of  fire" 
should  point  away  from  the  target. 

It  will  thus  be  seen  that  any  elevation  or  depression  in  degrees 
and  minutes  from  0  to  90°,  within  the  limits  imposed  by  the  method 
of  mounting,  can  be  given  by  this  quadrant.  It  will  be  noticed  that 
it  is  graduated  on  one  side  from  0  to  44°  and  on  the  other  from  45° 
to  89°.  The  extra  degree  on  both  sides  will  be  given  by  the  sliding 
level.  It  will  also  be  noticed  that  if  45°  be  given  on  the  one  side  by 
moving  the  arm  to  44°  and  the  index  on  the  level  to  60',  and  the  quadrant 
be  then  placed  to  give  readings  above  45°  without  changing  the  arm  or 
level,  it  will  still  record  45°;  for  the  position  of  the  level  to  give  a  reading 
of  60'  above  44°  is  also  the  position  to  give  a  reading  of  0'  above  45°, 
and  the  main  index  will  be  found  to  stand  at  45°  on  the  opposite  side 
of  the  graduated  arc. 


396  THE  SERVICE  OF  COAST  ARTILLERY 

Model  of  1898. — The  method  of  setting  this  quadrant  for  a  given 
reading  is  the  same  as  in  the  other  models,  using  the  graduation  on 
either  side  of  frame.  Its  use  is  simplified  in  that  it  is  only  necessary 
after  having  set  it  for  a  given  angle  of  elevation  or  depression  to  place 
it  on  its  seat  on  the  gun  with  the  arrow  marked  "  Line  of  fire,  elevation," 
or  "  Line  of  fire,  depression/'  as  the  case  may  be,  pointing  toward  the 
target. 

CRUSHER  GAUGE 

The  crusher  gauge  for  seacoast  cannon  is  used  for  determining  the 
maximum  pressure  exerted  in  the  bore  of  the  gun  during  service  firing. 
Pressures  are  required  to  be  taken  not  only  at  proof  firings  and  tests 


FIG.  61.— Crusher  Gauge  Outfit. 

of  powder  and  ammunition,  but  also  in  service  target  practice.  There 
are  three  standard  outfits  of  crusher  gauges,  namely,  those  for  large- 
caliber  guns,  those  for  intermediate,  and  those  for  small-caliber  guns. 

The  outfit  used  for  large-caliber  guns  is  shown  in  Fig.  61,  and  is 
designed  for  use  in  all  cannon  above  6  inches  in  caliber. 

The  gauge  is  inserted  in  the  mushroom  head  of  the  breechblock  in 
each  gun,  two  crusher  gauges  being  us  d.  ^  blank  plug  similar  in 
external  appearances  to  the  crusher  gauge  is  furnished  to  protect  the 
gun  when  the  regular  gauge  is  not  in  its  seat.  This  may  be  seen  by 
referring  to  Plate  X. 


INSTRUMENTS,  DEVICES  AND  CliVRTS  397 

To  Prepare  Crusher  Gauge  for  Use,  the  closing  cap  is  removed  by 
holding  the  housing  fast  with  the  housing  wrench  in  the  left  hand  and 
unscrewing  the  closing  cap  with  the  closing-cap  wrench  in  the  right  hand. 
In  the  medium-caliber  crusher  gauge  outfit  the  teat  wrench,  the  tee, 
and  reamer  wrench  are  used  in  place  of  the  housing  and  closing-cap 
wrenches  respectively.  The  piston  is  pushed  out  with  the  gas-check 
inserting  tool.  The  piston  and  the  interior  of  the  crusher  gauge  should 
then  be  thoroughly  cleaned  with  oil  and  cotton  waste  and  freed  from 
moisture.  It  should  also  be  determined  that  the  piston  enters  the  bore 
freely  at  both  ends.  The  parts  of  the  crusher  gauge  being  in  order, 
put  a  drop  of  oil  on  each  end  of  the  piston  and  insert  piston  in  the  bore. 
Take  the  pressure  cylinder  which  is  to  be  used  in  recording  the 
pressure  and  enter  it  in  the  cylinder  holder  until  it  is  held  in  the 
middle  of  its  length.  Then  insert  pressure  cylinder  in  the  crusher  gauge 
with  the  fingers  so  that  it  rests  on  end  in  the  center  of  the  piston. 
Place  the  washer  on  top  of  the  housing  and  screw  in  the -closing  cap, 
setting  it  up  tightly  by  means  of  the  wrenches.  The  gas  check  is  then 
placed  in  the  bore  above  the  piston,  bottom  of  the  cap  next  to  the  piston, 
and  with  the  gas-check  inserting  tool  set  it  down  on  the  piston  until 
there  is  no  play  between  piston  head  and  pressure  cylinder  underneath, 
which  should  now  remain  firmly  held  between  piston  head  and  closing 
cap.  The  crusher  gauge  is  now  ready  for  insertion  in  the  gun. 

After  firing  dip  the  crusher  gauge  into  a  bucket  of  water  to  remove 
fouling  and  then  wipe  dry.  Unscrew  the  closing  cap,  using  the  wrenches 
as  above  described;  shake  pressure  cylinder  and  cylinder  holder  out 
of  the  gauge  and  push  the  piston  and  gas  check  out  with  the  gas-check 
inserting  tool.  Remove  the  cylinder  holder  from  the  pressure  cylinder, 
wipe  the  latter  clean,  and  place  it  in  the  properly  numbered  hole  in 
the  chest,  or  measure  it  immediately  if  time  is  available.  The  piston 
and  interior  of  crusher  gauge  should  then  be  cleaned  and  oiled  as  pre- 
viously described  before  again  being  inserted  in  the  gun.  A  new  pressure 
cylinder  and  generally  a  new  gas  check  will  be  required  for  each  round. 
The  washers  should  be  carefully  inspected  for  cracks  or  unusual 
hardening  of  the  metal  before  being  used. 

Pressure  Cylinders. — Two  sizes  of  pressure  cylinders  are  furnished, 
the  larger  being  designated  the  cannon-pressure  cylinder,  and  the 
smaller,  the  small-arms  pressure  cylinder;  the  latter  being  used  in 
minor-caliber  crusher-gauge  outfits.  These  cylinders  are  made  from 
copper  rods,  about  99  per  cent  pure  copper.  The  rod  is  drawn  once 
after  annealing  and  every  precaution  in  composition  and  treatment  is 
taken  to  make  the  metal  homogeneous. 


398  THE  SERVICE  OF  COAST  ARTILLERY 

These  cylinders  are  subjected  to  initial  compressions  of  from  2,000 
to  7,000  pounds  per  square  inch  less  than  the  standard  maximum 
powder  pressure  expected  in  the  guns  in  which  they  are  used,  the  object 
being  to  reject  all  pressure  cylinders  which  do  not  come  within  certain 
prescribed  limits  of  variation  in  set  (shortening)  due  to  this  com- 
pression, and  to  eliminate  abnormal  results  by  reducing  the  amount 
of  set  produced  by  the  powder  pressure.  These  cylinders  are  made 
up  in  lots  of  several  thousand  and  tarage  tables  are  prepared  for  the 
various  lots.  Pressure  cylinders  are  measured  by  the  micrometer 
before  and  after  firing,  and  the  amount  of  compression  is  the  difference 
between  these  readings.  In  making  these  measurements  care  should 
be  taken  to  secure  a  light  but  firm  contact  of  the  measuring  surfaces 
at  the  ends  of  the  pressure  cylinder.  They  should  not  be  squeezed. 
After  the  set  in  inches  is  obtained  by  subtracting  the  length  "  after 
firing"  from  the  length  " before  firing"  and  obtaining  the  set  in  inches 
from  the  pressure-record  pamphlet,  the  tarage  table  should  be  entered 
and  the  corresponding  pressure  obtained. 


TIME-RANGE    BOARD 

The  time-range  board  is  a  device  to  provide  information  for  keeping 
the  piece  laid  continuously  for  range,  so  that  if  an  observation  is  lost 
or  the  rate  of  change  in  range  received  from  the  plotting  room  indicates 
an  error,  the  range  setter  may  look  at  the  board  and  set  the  range  on 
the  range  scale,  on  the  carriage  of  the  gun,  in  accordance  with  the  data 
indicated  thereon.  It  is  placed  on  the  emplacement  wall  (when 
actually  in  use)  at  a  point  where  it  can  be  plainly  seen  by  the  range 
setter.  It  is  operated  by  the  range  keeper,  on  data  received  from  the 
plotting  room. 

The  board  is  shown  in  Fig.  62.  It  consists  of  an  oblong  frame 
containing  a  thousands  scale,  with  two  reading  openings.  This  scale 
is  numbered  from  11  to  1  on  the  left-hand  end,  and  from  2  to  12  on 
the  right-hand  end.  It  is  operated  by  moving  a  knob  in  the  slot  on 
the  upper  portion  of  the  board. 

A  hundreds  scale  running  the  length  of  the  board  is  marked  on  its 
outer  surface  just  under  the  reading  openings  of  the  thousands  scale. 
The  hundreds  scale  is  graduated  so  that  readings  300  yards  greater  or 
less  than  the  number  indicated  in  the  reading  openings  of  the  thousands 
scale  may  be  obtained. 

Below  the  hundreds  scale  and  extending  the  length  of  the  board 


INSTRUMENTS,  DEVICES  AND  CHARTS 


399 


there  is  a  plug  rack  with  holes  which 
divide  the  hundreds  scale  into  ten- 
yard  divisions. 

A  prediction  scale  graduated  from 
0  to  350  yards  in  both  directions  slides 
in  a  groove  underneath  the  plug  rack 
of  the  board. 

To  Use  the  Board. — The  first  cor- 
rected range  received  from  the  plotting 
room  is  indicated  on  the  board  by 
the  operator.  The  left-hand  reading 
opening  is  used  when  the  range  is 
increasing,  and  the  right-hand  read- 
ing opening  is  used  when  the  range 
is  decreasing. 

For  example :  Assume  the  first  cor- 
rected range  to  be  5,430  yards,  target 
moving  out.  The  thousands  scale  is 
moved  until  the  figure  5  appears  in 
the  left-hand  reading  opening.  The 
zero  of  the  prediction  scale  is  then 
moved  directly  under  the  third  hole 
from  the  right  of  figure  4  on  the  hun- 
dreds scale  and  a  plug  inserted.  At 
the  next  reading  sent  to  the  gun  and 
called  out,  say  5,580,  the  zero  of  the 
prediction  scale  is  moved  until  it  is 
directly  under  the  eighth  hole  to  the 
right  of  figure  5  on  the  scale  for  hun- 
dreds and  a  plug  inserted.  The  pre- 
diction scale  is  then  read  between 
plugs,  that  is  from  zero  of  the  predic- 
tion scale  back  to  the  first  plug  insert- 
ed. The  reading  will  be  found  to  be 
150,  in  other  words  the  range  to  the 
target  is  uniformly  increasing  at  the 
rate  of  150  yards  every  15  seconds, 
or  every  predicting  interval.  There- 
fore the  range  for  one  prediction  ahead 
will  be  indicated  under  the  reading 
150  to  the  right  of  zero  on  the  predic- 


lOa 


CD  O- 


CD- 


iOO  THE  SERVICE  OF  COAST  ARTILLERY 

tion  scale,  or  as  5,730.  A  plug  is  therefore  inserted  in  the  third  hole 
to  the  right  of  7  on  the  scale  for  hundreds.  The  operation  above 
given  is  repeated  as  each  range  is  received  and  the  rear  plugs  taken 
out. 

The  board  is  used  in  a  similar  manner  in  the  case  of  a  target  coming 
toward  the  battery  or  when  the  range  is  decreasing;  for  example,  suppose 
the  first  range  received  to  be  6,600  and  the  second  6,500.  A  plug  is 
inserted  under  the  6  of  the  scale  for  hundreds  and  when  the  second 
range  is  called  out  the  zero  of  the  prediction  scale  is  set  directly  under 
5  of  the  scale  for  hundreds  as  shown  on  plate  and  a  plug  inserted.  The 
reading  between  plugs  (from  zero  to  right)  will  be  found  to  be  100 
and  as  the  range  is  decreasing  a  plug  should  be  inserted  above  1 
(100)  to  the  left  of  zero  on  the  prediction  scale. or  directly  under  4  of 
the  hundreds  scale;  the  combined  reading  of  the  board  will  then  be 
6,400. 

POWDER   CHART 

The  powder  chart  is  used  to  determine  the  velocity  to  be  expected 
from  a  given  charge  of  powder  considered  as  a  function  of  the  temper- 
ature of  the  powder.  It  is  shown  in  Fig.  63. 

The  chart  consists  of  a  board  upon  which  the  chart  is  mounted; 
along  thfe" top  edge  of  the  board  a  T  square  fits  into  a  groove  which  runs 
the  length  of  the  board.  Along  the  top  edge  of  the  chart  a  velocity 
scale  is  marked,  with  graduations  to  represent  10  foot-seconds  to  the 
inch.  The  scale  reads  from  left  to  right  with  the  normal  velocity  of 
the  gun  placed  in  the  middle  and  designated  by  a  vertical  line  extending 
the  width  of  the  chart.  A  convenient  length  for  the  chart  is  20  inches, 
which  allows  for  a  variation  of  100  foot-seconds  on  each  side  of  the 
normal. 

Across  the  face  of  the  chart  is  drawn  a  temperature-velocity  curve 
plotted  to  rectangular  co-ordinates.  The  ordinates  are  the  temperatures 
and  the  abscissae  are  the  corresponding  variations  from  the  normal 
muzzle  velocity. 

The  left  edge  of  the  T  square  is  graduated  in  degrees  Fahrenheit, 
beginning  at  — 10  degrees  at  the  bottom  and  ending  at  100  degrees  at  the 
top.  A  convenient  scale  is  10  degrees  to  the  inch,  which  requires  a 
chart  about  13  inches  wide. 

A  horizontal  line  extends  across  the  chart  so  that  it  will  pass 
through  the  70°  mark  on  the  T  square;  this  line  designates  the  normal 
temperature. 


INSTRUMENTS,  DEVICES  AND  CHARTS 


401 


To  Use  the  Chart. — For  powder  tested  to  give  the  normal  velocity 
of  the  chart  at  70°  F.,  the  T-square  is  set  so  that  the  actual  temperature 
as  indicated  on  the  scale  of  the  T  square  lies  on  the  temperature  velocity 
curve,  and  the  velocity  that  may  be  expected  from  such  powder  will 
be  indicated  on  the  velocity  scale  at  the  top  of  the  chart,  at  the  inter- 
section of  the  left  edge  of  the  T  square  and  this  scale. 

For  powder  tested  and  adjusted  to  give  the  normal  velocity  at  any 
other  temperature  than  70°,  the  T  square  is  set  for  the  temperature 
at  which  the  powder  was  tested  and  the  velocity  read  as  in  the  first 


n 


£r 


Normal Temperature 


-too 

•90 
•80 
•70 


POWDEIH 


FIG.  63. 

case.  The  T  square  is  then  set  for  the  actual  temperature  of  the  powder 
and  another  velocity  determined.  The  difference  between  the  first 
velocity  obtained  and  the  velocity  obtained  from  the  temperature 
setting  will  give  the  algebraic  difference  to  be  added  to  the  normal 
velocity  for  the  gun  in  question,  and  the  same  will  be  the  velocity 
to  be  expected  from  the  charge  used. 

For  example:  Assume  that  the  normal  velocity  is  2,250  f.s.  The 
velocity  obtained  by  setting  the  T  square  at  the  test  temperature  was 
2,240  f.s.  The  velocity  for  temperature  setting,  or  the  actual  temper- 
ature of  the  powder  in  question,  say,  is  2,280  f.s.  The  difference 
would  then  be  +40  f.s.;  or,  this  added  algebraically  to  the  normal 
velocity  would  give  2,290  f.s.  as  the  probable  velocity  to  be  expected 
from  the  powder  in  question. 


CHAPTER  VIII 
SEARCHLIGHTS 

IN  developing  the  maximum  efficiency  of  searchlights,  when  acting 
in  conjunction  with  fixed  defenses,  the  following  requirements  are 
suggested  by  a  recognized  expert  on  searchlight  defense.* 

They  should  be  located  with  consideration  to  their  ability  to  search 
effectually  the  approaches  of  the  battle  area,  with  a  view  to  the  early, 
discovery  and  identification  of  the  enemy.  For  this  purpose  advanced 
roving  lights  on  portable  or  disappearing  towers  should  be  placed  some 
4,000  yards  in  front  of  the  outside  line  of  the  primary  armament,  where 
practicable,  and  observers  placed  still  further  to  the  front  and  in 
telephonic  communication  with  the  battle  commander.  The  purpose 
of  this  is  obvious  when  it  is  remembered  that  the  effective  range  of  the 
primary  armament  is  12,000  yards,  while  that  of  the  60-inch  light  is 
approximately  8,000  yards,  as  shown  in  the  accompanying  table. 

The  second  consideration  is  their  ability  to  illuminate  continuously 
with  minimum  interference,  a  number  of  targets  simultaneously  in. 
any  part  or  parts  of  the  battle  area.  This  can  be  accomplished  by  so 
disposing  the  lights  that  as  the  target  passes  in  through  successive  zones 
of  the  battle  area  it  can  be  picked  up  and  covered  by  searchlights 
assigned  to  each  zone  before  it  is  out  of  reach  of  the  lights  of  the  preced- 
ing zone.  Further  to  prevent  interference,  the  lights  should  be  placed 
on  the  flanks  of  all  stations  and  guns  pertaining  to  their  respective 
zones. 

The  third  consideration  concerns  the  ability  of  the  lights  to  illuminate 
landing  positions  and  points  from  which  the  fortifications  could  be 
readily  attacked  from  the  flanks  or  rear  by  raiding  parties  of  the  enemy. 
This  condition  may  be  overcome  by  a  judicious  employment  of  the 
outermost  roving  lights,  or  other  lights  in  special  positions,  and  when 


*  Namely,  Major  W.  C.  Davis,  C.  A.  C.,  II.  S.  A.,  from  whose  article,  published  in 
the  Journal  of  the  U.  S.  Artillery,  May-June,  1909,  most  of  the  information  in 
regard  to  the  tactical  use  of  searchlights  is  drawn. 

402 


SEARCHLIGHTS  403 

necessary,  supplemented  by  portable  lights,  controlled  by  the  coast 
artillery  supports,  along  the  land  front. 

The  fourth  consideration  is  their  ability  to  cover  mine  fields  and 
channels  leading  to  inner  harbors  against  the  operation  of  torpedo 
boats  and  other  craft.  This  condition  is  met  by  having  a  number  of  36- 
inch  lights,  on  sights  from  15  to  25  feet  above  high  water,  with  beams 
held  fixed  or  nearly  so,  across  the  channel,  or  covering  the  mine  field 
and  its  approaches.  .Where  channels  are  narrow,  diverging  lenses 
can  be  used.  The  36-inch  projector  is  effective  under  good  weather 
conditions  up  to  3,000  yards,  using  a  concentrated  beam  (angular 
divergence  about  2£  degrees).  At  this  range  the  beam  has  a  diameter 
of  approximately  120  yards.  At  2,000  yards  and  at  1,500  yards  the  same 
intensity  of  illumination  can  be  obtained  (as  with  the  concentrated  beam 
at  3,000  yards)  by  employing  lenses  giving  12  to  40  degrees'  divergence. 
Such  lenses  should  be  employed,  in  good  weather,  to  increase  the  time 
required  by  a  vessel  to  traverse  the  beam. 

Another  consideration  of  importance  in  connection  with  the  search- 
light defense  is  the  providing  of  relieving  lights  to  replace  lights 
temporarily  or  permanently  disabled.  This  can  be  accomplished  either 
by  having  duplicate  lights  installed  whenever  practicable,  or  by  assign- 
ing one  light  to  another's  relief. 

The  effective  protection  of  advanced  searchlights  from  capture 
or  destruction  by  the  enemy  must  also  be  considered.  In  this  con- 
nection no  searchlight  should  be  advanced  so  far  to  the  front,  or 
otherwise  sited,  that  an  armored  ship  can  attack  it  effectively  without 
exposing  herself  to  destruction  from  the  high-power  guns  of  the  forti- 
fications. At  night  a  searchlight  is  a  very  difficult  target  to  hit,  and 
when  properly  made  and  emplaced  can  only  be  put  out  of  action  by  a 
direct  hit  on  the  projector.  It  is  believed  this  is  not  likely  to  occur 
until  the  vessel  has  advanced  to  close  range,  say  about  2,500  yards, 
where  its  secondary  armament  can  be  used  to  full  advantage.  Should 
the  enemy,  under  these  conditions,  succeed  in  obtaining  the  range, 
so  that  the  projector  should  appear  to  be  endangered,  the  light  should 
be  suddenly  occulted — leaving  no  target  for  him  to  fire  at,. and  probably 
leading  him  to  the  false  conclusion  that  the  projector  had  been  destroyed 
or  disabled.  Under  such  conditions  the  advanced  light  has  served  its 
purpose,  for  it  has  revealed  the  enemy,  who  should  now  be  covered  by 
a  searchlight  further  to  the  rear.  If  the  advanced  light,  as  previously 
suggested,  is  placed  not  more  than  4,000  yards  in  front  of  the  first  line 
of  primary  armament,  the  ship,  when  she  has  closed  to  within  2,500 
yards  from  the  light,  would  be  less  than  6,500  yards  from  the  primary 


404  THE  SERVICE  OF  COAST  ARTILLERY 

armament  of  the  defense — a  situation  which  she  should  not  be  able 
to  maintain  for  any  appreciable  time. 

All  advanced  searchlights  should  be  protected  from  torpedo  boats 
and  small  craft  by  a  suitable  force  of  coast  artillery  supports,  supple- 
mented by  a  few  field  guns.  In  the  daytime  these  lights  should  be  run 
under  cover  and  their  position  concealed  from  the  enemy. 


TYPES    OF    PROJECTORS 

The  number  of  searchlights  necessary  for  the  proper  illumination  of 
the  water  area  covered  by  any  particular  fort  depends  upon  the  size 
of  the  area  in  question  and  the  importance  attached  to  its  defense. 
Two  types  of  projectors  have  been  adopted  in  the  U.  S.  Coast  Artillery 
service,  namely  the  36-inch  and  the  60-inch.  Both  of  these  types 
are  provided  with  parabolic  reflectors.  The  beam  proceeding  from 
them,  even  when  the  arc  is  most  perfectly  in  focus,  is  not  a  cylinder,  but 
the  frustrum  of  a  cone;  the  36-inch  light  having  an  angular  divergence 
of  2^  degrees,  and  the  60-inch  light  a  divergence  of  from  2^  to  3  degrees, 
from  the  projector  outward.  The  approximate  diameter  of  the  beam 
at  various  ranges  is  shown  in  the  following  table: 

Range,  yards  ..............      1000     2000     3000     4000     5000     6000     7000     8000 

36-inch  \  ,.  ,,  f    ,    ,       40         80       120       160       200       240       280       320 

80       50       100       150       200       250       300       350       400 


From  this  table  it  will  be  seen  that  the  illuminating  power  of  the 
beam  follows  the  quadric  law,  varying  inversely  with  the  square  of  the 
distance. 

In  passing  through  the  air  the  elements  of  the  beam  encounter 
various  impurities,  such  as  particles  of  moisture,  dust,  carbon,  etc., 
which  absorb,  reflect,  and  refract  rays  of  the  light,  causing  the  beam 
to  fall  off  rapidly  in  intensity  and  giving  rise  to  a  considerable  amount  of 
diffused  light.  Due  to  this  cause  the  beam,  as  it  passes  through  the 
air,  is  visible;  its  distinctness  varying  inversely  with  the  clearness  of 
the  atmosphere,  and  directly  with  the  darkness  of  the  night. 

The  diffused  light  above  referred  to,  radiating  at  right  angles  from 
the  beam,  lights  up  with  considerable  brightness  objects  two  or  three 
hundred  yards  from  the  beam,  and  when  the  beam  is  held  just  above 
the  water,  gives  rise  to  the  "  reflected  ray"  or  beam,  so  often  observed 
and  mentioned  in  the  coast  artillery  service.  The  clearer  the  atmos- 
phere and  the  brighter  the  direct  beam  from  the  searchlight,  the  less 


PLATE   XXXV 


36-inch  Searchlight  (Proiector).     Showing  movable  truck,  and  apparatus 
for  electrical  control. 


SEARCHLIGHTS  405 

luminous  becomes  the  "reflected  beam";  but  in  no  case  does  the 
"reflected  beam"  ever  approach  the  brightness  of  the  direct  beam; 
and  a  target  passing  through  the  "reflected  beam"  is  never  seen  as 
clearly,  other  conditions  being  the  same,  as  it  would  appear  in  the  direct 
beam  of  the  light. 

The  atmospheric  conditions  affecting  the  penetration  of  the  search- 
light beam  are  the  same  as  those  affecting  sunlight;  that  is,  fog,  mist, 
snow,  rain,  smoke,  etc.,  reduce  the  effective  range  of  the  beam  in  pro- 
portion to  their  respective  densities. 

Xo  definite  rule  can  be  made  as  to  the  exact  range  at  which  a  target 
in  a  searchlight  beam  should  be  visible,  the  range  varying  with  respect 
to  the  condition  of  the  air;  the  intensity  of  the  light;  the  color  and 
shape  of  the  target;  the  position  of  the  observer  with  respect  to  the 
target  and  light;  the  ability  of  the  observer;  the  suitability  of  the 
telescope;  and  the  character  of  the  background. 

Atmospheric  conditions  are  at  their  best  when  the  air  is  free  from 
moisture  and  smoke,  and  when  the  moon  and  stars  are  entirely  obscured 
by  clouds.  The  beam  then  has  great  penetration  and  the  law  of 
contrast  brings  the  target  out  into  clear  relief. 

The  intensity  of  the  light  depends  directly  upon  the  candle  power. 
The  average  intensities  of  the  German  projectors,  using  125  to  150 
amperes,  are  61,000,000  and  180,000,000  standard  candle-power, 
respectively;  that  is,  the  60-inch  projector  has  three  times  the  candle- 
power  of  the  36-inch  projector. 

When  a  searchlight  beam  impinges  on  a  ship  a  portion  of  the  light 
is  absorbed,  while  the  balance  is  reflected  in  various  directions,  according 
to  the  well-known  law  that  the  angle  of  reflection  is  equal  to  the  angle 
of  incidence.  The  percentage  of  light  absorbed  depends  upon  the  color 
and  kind  of  paint  and  the  character  of  the  reflecting  surface.  Thus  a 
dark-colored  ship  is  less  conspicuous  than  one  painted  white,  and  a  ship 
the  lines  of  which  are  irregular  and  broken  is  not  as  conspicuous  as 
one  having  a  smooth  outline. 

All  stations  and  guns  using  the  same  type  of  illuminating  light 
should  be  on  the  same  side  of  the  light  and  the  light  should  be  con- 
trolled from  that  side.  The  projector,  for  efficient  service,  should  not 
be  less  than  150  yards  from  the  flank  of  the  nearest  battery  or  position 
finder  that  the  searchlight  is  to  serve.  That  within  any  practicably 
attainable  range  in  elevation  (other  conditions  remaining  constant) 
the  greater  the  difference  in  level  between  the  observer  and  the  search- 
light, the  better  the  illumination  of  the  target — always  excepting  the 
case  where  the  observer  or  the  projector  is  so  near  the  water  as  to  be 


406 


THE  SERVICE  OF  COAST  ARTILLERY 


interfered  with  by  the  curvature  of.  the  earth.  It  may  be  stated  that 
the  two  greatest  objections  to  the  high-siting  of  searchlights  in  the 
U.  S.  Coast  Artillery  service,  are:  (1)  That  it  may  give  too  great  a 
"searchlight  dead  space/'  so  called  when  the  beam  is  projected  so  as 
to  strike  the  water  at  a  certain  range,  inside  of  which  vessels  may  pass 
under  the  beam  unilluminated  and  unobserved.  (2)  High-sited 
searchlights  are  of  no  value  whatever  in  harbors  where  high  fog  prevails 
— where  the  water  underneath  may  be  perfectly  open  for  navigation. 

The  ability  of  the  observer  usually  depends  upon*  the  amount  of 
practice  he  receives  at  night.  A  good  illustration  of  the  influence  of 
training  is  seen  in  pilots  of  boats  at  night  or  where  fog  is  prevalent. 
The  acuteness  of  vision  by  which  a  pilot  will  discern  landmarks  at  night 
or  through  a  fog  seems  wonderful  to  a  landsman,  who,  standing  by  his 
side,  is  unable  to  see  anything. 

Experience  teaches  that  the  best  telescope  for  night  work  is  one 
with  a  large  objective  and  low  magnifying  power. 

Channels  whose  hilly  shores  are  rough  and  irregular,  or  are  heavily 
wooded,  offer  special  difficulties  for  observers,  as  do  also  the  shadows 
thrown  on  the  water  by  high  hills  or  mountains.  These  difficulties 
are  apparent  in  the  daytime  and  at  night  are  even  more  in  evidence. 
Under  such  conditions,  a  small  dark-painted  craft,  like  a  torpedo  boat, 
stealing  in  close  to  the  shore,  is  a  most  difficult  object  to  detect. 


APPROXIMATE    RANGES 

The  following  table  summarizes  the  approximate  ranges  at  which 
targets  should  be  visible  in  good  weather,  and  under  other  favorable 
conditions. 


Color  of  ship. 

Vessel  seen,  but 
outline  obscure. 

Form  clear  enough 
for  horizontal 
tracking.    , 

Target  can  be 
water-  lined. 

36" 

60" 

36" 

60" 

36" 

60" 

White  
'•War  paint"  

8000 
6000 
5000 

12000 
9000 
7000 

5500 
4500 
4000 

8000 
6500 
5500 

4500 
4000 
3500 

6500 
6000 
4500 

Black 

The  service  of  searchlights  is  officially  defined  in  the  U.  S.  Coast 
Artillery  Drill  Regulations. 


SEARCHLIGHTS  407 


COMPONENTS   OF   SEARCHLIGHTS 

In  addition  to  their  tactical  classification  searchights  are  classified 
with  reference  to  the  size  of  their  mirrors  or  reflectors.  The  two 
standard  sizes  found  in  the  U.  S.  Coast  Artillery  service  are,  as  previously 
stated,  the  36-  and  60-inch.  The  standard  36-inch  light,  with  apparatus 
for  electrical  control,  etc.,  is  shown  in  Plate  XXXV. 

The  principal  parts  of  a  searchlight  are  the  lamp,  mirror,  drum, 
lamp  box,  glass  front  door,  standards,  pedestal,  turntable,  training 
mechanism. 

(a)  Lamp. — The  lamp  of  the  latest  type  of  searchlight  in  service 
is  shown  in  Plate  XXXVI,  and  its  mechanism  is  as  follows: 

A,  negative  carbon  holder; 

B,  positive  carbon  holder; 

C,  clamping  screws  for  carbon  clamps; 

D,  vertical  adjusting  screw  for  positive  carbon  clamp; 

E,  horizontal  adjusting  screw  for  positive  carbon  clamp; 

F,  negative  carbon  support; 

G,  positive  carbon  support; 
H,  lamp  frame; 

K,  main  lamp  contact  shoes; 
L,  hand  feed  screw; 
Af,  focus  nut  for  focusing  screw; 

N,  stud  of  lamp  switch  for  cutting  out  feeding  magnet; 
0,  ratchet  and  pawl; 
P,  feeding  magnet  armature; 
Q,  contact  of  circuit  breaker; 
R,  adjusting  screw  for  ratchet  arm; 
S,  starting  magnet; 
T,  feeding  magnet; 
U,  adjusting  spring  for  feeding  magnet. 

The  lamp  is  for  producing  the  light,  starting  and  feeding  the  arc,  and 
is  operated  through  its  mechanical  arrangement  by  the  electric  magnets 
named  in  the  nomenclature.  The  circuits  of  the  lamp  are  shown  in 
Figs.  64  and  65.  The  current  is  brought  to  the  searchlight  by  the 
power  cables  and  enters  the  pedestal,  going  directly  to  the  main  switch 
of  the  lamp;  from  there  it  is  taken  by  leads  to  the  contact  rings  attached 
to  the  turntable. 

There  are  two  circuits — the  series  circuit,  which  includes  the  arc, 


408 


THE  SERVICE  OF  COAST  ARTILLERY 


and  the  feed-magnet  circuit  in  shunt  with  it.  The  series  circuit  is 
from  the  positive  contact  shoe  to  the  series  magnet,  thence  through 
the  positive  carbon  holder  to  the  arc,  back  through  the  negative  carbon 
holder  to  the  negative  contact  shoe,  and  after  passing  through  the  series 


FIG.  64. — Circuits  and  Lamp  Mechanism 

magnet  the  circuit  is  connected  to  the  frame,  the  frame  being  a  part  of 
the  circuit.  The  feed  magnet  circuit  is  from  the  circuit-breaker  spring 
(positive)  to  the  other  circuit-breaker  contact,  then  to  the  feed  magnet 
and  through  the  main  switch  to  negative  line. 

The  Action  of  the  Lamp  is  as  Follows :  When  the  circuit  is  closed 
the  resistance  in  the  air  gap  prevents  any  current  from  flowing  in  the 
arc  circuit,  and  the  voltage  across  the  carbons  will  be  practically  that 
of  the  source  of  power.  This  difference  of  potential  or  pressure  causes 
sufficient  current  to  pass  in  the  shunt  circuit,  so  that  the  feed  magnet 


SEARCHLIGHTS 


409 


attracts  its  armature  and  thus  draws  the  pawl  into  the  ratchet  while 
turning  it  through  a  small  angle.  The  act  of  drawing  the  armature 
breaks  the  shunt  circuit  at  the  circuit-breaker  contact,  and  the  attrac- 
tion ceasing,  the  spring  returns  the  armature  to  its  initial  position.  The 


Circuit 


Feet/iflq   Ma j  nets 
*!__  Positive  Carbon 


io 
contact* 


FIG.  65. — Circuit  Breaker,  etc.,  Searchlight  Lamp  Mechanism. 


voltage  across  the  arc  is  not  changed  since  the  first  movement  of  the 
ratchet,  so  the  operation  will  be  repeated  and  continue  until  the  carbons 
touch  each  other.  When  the  carbons  touch  a  large  flow  of  current  makes 
the  starting  magnet  attract  its  armature,  which  operates  to  pull  the 


410  ,     THE  SERVICE  OF  COAST  ARTILLERY 

carbons  apart,  forming  the  arc.  It  takes  a  short  time  for  the  crater  to 
burn  properly,  and  until  this  is  done  the  arc  will  not  have  the  proper 
length.  As  soon  as  this  is  attained  the  feeding  magnet  will  keep  the 
carbons  the  proper  distance  apart,  since  it  acts  when  the  proper  voltage 
across  the  arc  is  exceeded,  this  adjustment  being  made  by  the  spring 
attached  to  the  feed  magnet  armature. 

The  attractive  power  of  the  magnet  depends  urjon  the  current 
passing  around  the  core,  which  necessarily  is  proportional  to  the 
difference  of  voltage  across  the  arc  and  the  resistance  of  the  magnet 
winding.  The  feed  spring  is  arranged  to  resist  an  opposing  force  equal 
to  the  force  of  attraction,  so  that  whenever  this  force  is  exceeded 
which  indicates  that  the  voltage  across  the  arc  has  been  exceeded 
and  that  the  carbons  are  too  far  apart,  the  current  will  flow 
around  the  feed  magnet  and  the  feeding  magnetism  will  commence 
to  operate,  feeding  the  carbons  closer  together  and  maintaining  the 
proper  arc. 

(6).  The  Arc. — If  two  pieces  of  carbon  are  joined  by  wires  to  the 
terminals  of  a  battery  of  sufficient  electro-motive  force,  or  to  a  generator 
of  electric  current  as  just  described,  and  are  then  brought  into  contact 
for  a  moment  and  drawn  apart  a  short  distance,  as  is  done  with  the 
lamp  of  a  searchlight,  a  kind  of  electric  flame  called  the  electric  arc 
or  voltaic  arc  is  produced  between  the  points  of  the  carbons,  and  a 
brilliant  light  is  given  off  by  the  white-hot  points  of  carbon  electrodes. 
Before  contact  of  the  carbons  is  made  the  difference  of  potential  or 
pressure  between  the  points  is  insufficient  to  cause  a  spark  to  leap 
across  even  1/10,000  of  an  inch  of  air  space,  but  when  the  carbons  are 
made  to  touch  by  the  feeding  mechanism  of  the  lamp  a  current  is 
established.  On  separating  the  carbons  the  spark  at  parting  volatilizes 
a  small  quantity  of  carbon  upon  the  points.  This  carbon  vapor,  being  a 
fairly  good  conductor,  allows  the  current  to  continue  to  flow  across 
the  gap,  provided  it  is  not  too  wide,  and  as  the  carbon  vapor  has  a 
high  resistance  it  becomes  intensely  heated  by  the  passage  of  this 
current,  and  the  carbon  points  become  highly  heated,  giving  off  a 
white  light.  The  temperature  of  the  arc  at  this  point  is  estimated  to 
be  6.000  degrees  C.  The  greater  part  of  the  light  is  given  off  from  the 
points  of  the  carbons  themselves,  though  their  temperature  is  not  as 
high  as  the  arc,  due  to  the  principle  that  solid  matter  is  a  better  radiator 
than  gaseous.  The  volatilizing  from  the  positive  electrode  or  carbon 
causes  it  to  become  hollowed  out  or  cup-shaped,  forming  the  crater. 
Due  to  the  gap  between  the  two  carbons  being  small,  particles  of  the 
volatilized  carbon  are  deposited  on  the  negative  carbon,  and  this  tends 


SEARCHLIGHTS  411 

to  point  it.  The  amount  of  light  emitted  from  the  crater  depends  upon 
the  amount  of  current  and  the  carbons  used;  that  is,  their  size,  or  the 
incandescent  area  exposed. 

The  normal  current  for  the  36-inch  light  is  130  amperes,  while  the 
normal  voltage  across  the  arc  is  60;  for  the  60-inch  light  the  normal 
current  is  200  amperes,  and  the  normal  voltage  across  the  arc  is  65. 
For  any  particular  light  it  may  be  found  that  better  practical  results 
are  obtained  by  slight  variations  in  the  values  given,  as  it  has  been 
found  in  practice  that  nearly  every  light  has  its  individual  factor. 
An  arc  may  be  made  and  maintained  by  either  direct  or  alternating 
current,  but  for  searchlight  purposes  an  arc  from  pure  carbon  electrodes 
supplied  with  direct  current  has  been  found  to  be  the  best,  and  is  the 
method  used  in  coast  defense. 

(c)  The  Mirror. — The  reflector  is  a  parabolic  mirror  and  its  object 
is  to  project  the  light  reflected  from  the  arc  in  parallel  rays  to  the 
target.     As  is  knoVn,  the  angle  made  by  a  reflected  ray  of  light  with 
the  normal  and  the  reflecting  surface  is  equal  to  that  made  by  the  incident 
ray,  so  by  the  use  of  a  parabolic  reflecting  surface,  when  the  light  is  in 
focus  the  reflected  rays  are  parallel. 

The  mirror  is  so  mounted  in  a  brass  frame  that  it  is  securely  pro- 
tected against  concussion,  and  provision  is  made  for  expansion  due  to 
heat.  The  mirror  should  always  be  kept  dry  to  prevent  spotting  or 
frost  due  to  moisture,  and  prior  to  its  use  should  be  cleaned  by  dusting 
with  a  soft  brush  or  with  a  piece  of  chamois  skin  after  it  has  been  care- 
fully shaken  out  to  prevent  the  presence  of  grit,  which  would  result 
in  scratching  the  mirror.  It  must  be  remembered  that  the  presence  of 
dirt  or  dust  will  greatly  reduce  the  amount  of  reflected  light.  It  has 
been  found  from  observation  that  the  direct  rays  of  the  sun  damage 
reflectors  to  a  considerable  extent,  therefore  they  should  not  be  exposed 
unnecessarily. 

(d)  The  Drum. — The  drum  and  lamp  box  are  together  a  casing  for 
the  lamp  and  reflector.     The  drum  is  pivoted  on  trunnions  that  bear 
on  standards  which   are  bolted  to  the  turntable.     It  can  be   given 
vertical  motion  on  the  trunnions  or  a  horizontal  motion  on  the  rollers, 
or  both  together,  such  being  necessary  for  training  the  beam.     The  lamp 
rests  on  guides  fastened  to  the  lamp  box,  so  arranged  as  to  be  moved 
forward  or  backward  by  turning  the  focusing  screw,  the  head  of  which 
is  shown  in  the  cut  referred  to. 

(e)  Lamp  Box. — The  lamp  box  is  shown  in  detail  in  Plate  XXXVI, 
and  is  used  to  carry  the  lamp  and  feeding  mechanism,  and  carries  the 
contacts  for  transmitting  the  current  to  the  lamp  proper. 


412  THE  SERVICE  OF  COAST  ARTILLERY 

(/)  Glass  Front  Door. — The  glass  front  door  is  provided  for  the 
protection  of  the  lamp  and  mirror.  It  is  made  up  of  a  circular  frame 
carrying  strips  of  glass  about  two  inches  wide  of  varying  lengths 
depending  upon  the  diameter  of  the  projector  considered. 

(g)  Standards. — The  light  is  provided  with  two  standards  or  up- 
right arms,  which  are  bolted  to  the  turntable  at  the  lower  extremity 
and  carry  the  trunnions  at  the  top,  supporting  and  carrying  the  drum 
and  its  contents  and  give  the  light  the  necessary  motions  for  training. 

(h)  Turntable. — A  turntable  attached  to  the  horizontal  training 
motor  through  a  gear  train  is  used  to  give  the  beam  horizontal  motion. 

(k)  Pedestal. — The  pedestal  is  that  part  of  the  light  beneath  the 
turntable  carriage.  On  its  interior  surface  the  training  motors  are 
arranged  to  give  both  the  horizontal  and  vertical  motions  of  the  beam. 

(1)  Training  Mechanism. — Training  normally  is  by  means  of  an 
electrically  controlled  mechanism,  but  there  is  an  auxiliary  mechanism, 
so  that  in  case  the  electric  control  fails  the  training  may  be  done  by 
hand  at  the  light. 

The  electric  control  consists  of  two  training  motors  located  in  the 
pedestal  and  connected  electrically  with  the  controller  located  in  the 
station  from  which  the  light  is  operated.  The  vertical  training  motor 
through  a  gear  train  transmits  a  vertical  motion  to  the  beam,  and  the 
horizontal  training  motor  through  a  gear  train  drives  a  pinion  which 
engages  with  the  pinion  on  the  turntable,  giving  the  beam  horizontal 
motion. 

ESSENTIALS   OF  EFFECTIVENESS 

The  essentials  of  an  effective  searchlight,  aside  from  its  tactical 
location,  may  be  stated  as  follows: 

a.  A  proper  power  supply. 

b.  Good  arc,  which  necessarily  means  good  carbons. 

c.  The  proper  focusing  of  the  beam. 

d.  Careful  operation  of  the  training  mechanism. 

e.  A  good  operator  of  the  searchlight  controller. 

The  first  depends  upon  the  installation  and  is  beyond  the  control  of 
those  ordinarily  charged  with  the  care  and  operation  of  searchlights. 
The  second  is  within  the  power  of  those  charged  with  the  care  and 
operation  of  the  searchlight,  and  the  steps  necessary  to  obtain  a  good 
arc  may  be  summarized  as  follows : 

1.  Begin  with  a  new  set  of  carbons. 


SEARCHLIGHTS  413 

2.  Secure  them  in  their  holders  with  the  negative  carbon — that  is, 
the  smaller  one — nearest  the  mirror. 

3.  See  that  they  are  in  alignment — that  is,  that  the  axis  of  the 
positive   carbon  is  approximately  in  prolongation  with   that   of  the 
negative.     Should  they  not  be  properly  aligned,  adjust  them  by  means  of 
the  adjusting  screws  indicated  in  Plate  XXXVI. 

Make  sure  that  the  carbons  are  clamped  securely,  so  that  when  the 
drum  is  elevated  they  will  not  be  thrown  out  of  alignment,  or  drop  back 
and  spread  the  arc,  giving  it  abnormal  length.  The  carbons  should  have 
about  f  of  an  inch  play  between  the  tips  when  separated.  Then  bring 
the  carbon  tips  approximately  in  the  focus  of  the  beam  by  means  of  the 
focusing  screw.  The  drum  is  marked,  that  is,  the  finder  in  the  drum 
is  marked  to  indicate  this  position.  If  the  start  is  made  with  carbons 
that  have  been  used  before  and  the  crater  is  not  evenly  formed,  part 
should  be  broken  off  and  reamed  out  before  the  start  is  made. 

5.  Feed  the  carbons  together  by  turning  the  feed  screw  until  they 
nearly  touch  and  turn  the  current  on. 

6.  Keep  the  current  as  near  normal  as  possible,  as  this  assists  the 
crater  in  forming  properly. 

7.  After  the  lamp  has  been  operated  long  enough  for  all  parts  to  reach 
their  normal  temperature  and  the  arc  has  become  normal,  run  the 
carbons  apart  slowly  and  note  the  voltmeter  reading  at  the  first  stroke 
of  the  magnet.     If  the  voltage  is  above  the  normal  voltage  as  given 
across  the  arc  for  the  lamp  in  question,  loosen  the  feed  spring  U  shown 
in  Plate  XXXVI,  until  proper  adjustment  is  made.     Should  the  volt- 
age  be    below   the  normal,  tighten  the  same  screw.     It  is  necessary 
that  this   adjustment  be   made  when  the  lamp  is  in  the  horizontal 
position. 

8.  Focus  the  lamp  by  bringing  the  arc  directly  on  the  cross  wires 
of  the  ground-glass  finder  and  note  if  the  rays  leave  the  mirror  parallel. 


CHAPTER  IX 
SUBMARINE  MINES,  SMALL  BOATS,  ETC. 

IN  case  of  heavy  fog,  or  at  night  when  an  attack  is  unexpected,  or 
even  when  expected,  the  possible  failure  of  searchlights  makes  it  impera- 
tive to  provide  some  final  means  of  defense.  An  adequate  submarine 
defense  has  been  developed  in  the  U.  S.  Coast  Artillery  service,  and 
consists  of  a  submarine  mine  containing  an  explosive  charge,  a  firing 
device,  and  the  necessary  arrangement  for  testing  and  signaling.  The 
whole  is  inclosed  in  a  water-tight  case,  and  is  intended  to  be  submerged 
in  the  waterway  or  entrance  to  important  harbors,  and  naval  bases. 

A  submarine  mine  is  not  a  torpedo,  although  frequently  referred  to 
as  such.  The  device  just  described,  when  submerged  the  proper  depth 
under  water,  and  anchored  in  position,  is  a  submarine  mine,  while  a 
torpedo  consists  of  a  case  containing  a  charge  of  explosive,  a  firing  device, 
and  a  device  for  propelling  it  through  the  water.  The  submarine  mine 
is  fixed  in  position,  and  its  functions  are  purely  defensive,  while  the 
torpedo  is  both  defensive  and  offensive. 

Submarine  mines  are  of  two  distinct  classes  with  regard  to  their  use 
in  respect  to  position,  and  are  classified  as  buoyant  and  ground  mines. 
The  buoyant  mine  is  one  that  floats  in  position,  and  has  such  an  excess 
of  buoyancy  that  if  it  were  not  anchored  in  position  as  shown  in  Fig. 
66,  it  would  float  on  the  surface.  These  mines  are  designed  to  be 
submerged  and  held  in  position  by  anchors.  A  ground  mine  consists  of 
a  case  containing  an  explosive  and  a  firing  device,  and  is  heavier  than 
the  amount  of  water  it  displaces,  and  therefore,  requires  no  anchor, 
and  sinks  to  the  bottom. 

Mechanical  and  Electrical  Types. — Submarine  mines  are  further 
classified  as  mechanical  or  electrical,  depending  upon  their  means  of 
firing. 

A  mechanical  mine  is  a  non-controllable  mine,  and  may  be  either 
electrical  or  purely  mechanical.  They  carry  their  own  firing  apparatus, 
and  when  once  planted,  are  equally  dangerous  to  our  own  and  to  the 
enemy's  vessels.  They  are  non-controllable  to  such  an  extent,  and  such 

414 


SUBMARINE   MINES,   SMALL   BOATS,   ETC. 


415 


ng   Buoy 
Distribution  JBoxJZuoy-  - 


.P/antrry  &uoy  f?o/>e. 


Mooring  Rope- 


— Distribution 


-Sf 


'*  c. 


tiple 
S.C  —  Ca'Je 


416  THE  SERVICE   OF  COAST   ARTILLERY 

a  menace  to  the  commerce  of  friendly  nations  and  non-combatants  that 
their  use  in  modern  warfare  is  rapidly  being  dispensed  with. 

The  electrical  mine  adopted  in  our  system  and  in  most  modern 
systems,  is  controllable  and  can  be  made  perfectly  safe  or  equally 
dangerous  by  the  manipulation  of  the  electrical  features.  The  electrical 
mine  is  arranged  so  that  it  may  be  fired  at  the  will  of  the  operator; 
on  contact  with  an  enemy's  vessel,  or  after  a  contact  and  a  signal  has 
been  given. 

To  properly  protect  the  entrance  to  a  harbor  or  naval  base,  it  is 
thought  that  at  least  three  lines  of  submarine  mines  a.e  essential. 
The  exact  location  of  these  different  lines  of  mines  involves  considera- 
tions with  reference  to  the  other  defenses  of  the  harbor  considered. 
Their  location  must  also  depend  upon  the  width  and  depth  of  the 
channel,  the  swiftness  of  the  current,  conditions  of  tide,  bottom,  and 
difficulties  of  planting. 

A  mine  field  must  be  properly  protected  by  shore  batteries  in  order 
to  become  effective.  Mine-fields  which  are  susceptible  to  raids  by 
the  enemy  may  be  considered  as  not  fulfilling  their  proper  function,  as 
their  protection  would  require  the  explosion  of  mines  when  tampered 
with,  which  is  not  the  proper  function  of  a  submarine  mine  defense. 
The  proper  protection  for  the  mine  fields  is  that  of  rapid-fire  shore 
batteries,  submarine  boats  and  torpedo  boats,  in  order  that  raiding 
parties  of  the  enemy  may  be  met  in  the  same  manner  in  which  such 
tours  are  ordinarily  carried  out. 

The  ideal  location  of  a  mine  field  would  be  that  which  would  require 
the  vessels  of  a  hostile  fleet  to  be  held  in  the  zone  of  most  effective  fire 
of  the  heavy  guns.  This  zone  lies  between  4,000  and  8,000  yards  from 
the  main  defenses  of  a  harbor,  and  is  beyond  the  interior  limit  of  effective 
mortar  fire.  It  can  readily  be  seen,  therefore,  that  any  mine  field 
which  would  break  up  the  formation  of  an  enemy's  fleet  in  this  effective 
zone,  in  addition  to  the  possibilities  of  the  total  destruction  of  the 
vessels  themselves  by  the  mines,  would  result  in  the  fleet  being  exposed 
to  the  destructive  fire  of  the  heavy  batteries  where  that  fire  is  most 
effective.  In  the  location  of  mine  fields  it  is  also  essential  that  the 
outer  line  be  sufficiently  extended  so  that  in  case  of  fog,  thick  weather, 
and  darkness,  the  presence  of  the  enemy  will  be  made  known  before 
it  is  too  late  to  prevent  an  effective  run-by. 

The  essential  elements  of  a  mine  command  consist  of  the  fire-control 
system,  the  rapid-fire  batteries,  the  mining  casemate,  the  loading  room, 
a  storehouse  for  mine  material,  sufficient  cable  tanks  for  the  storage 
of  submarine  mine  cable,  the  searchlight  system,  the  magazine  and 


SUBMARINE  MINES,   SMALL  BOATS,   ETC.  417 

explosives,  as  well  as  a  means  to  transport  and  handle  this  material,  the 
necessary  boats  for  carrying  out  the  duties  of  putting  the  mines  in 
position,  the  repair  of  the  mine  fields,  and  some  means  for  the  test, 
care  and  preservation  of  the  above  elements. 

The  Fire-Control  System. — The  fire-control  stations  of  a  mine  com- 
mand are  provided  with  range  finders,  and  in  the  mine  primary  station 
a  telescope,  a  plotting  board,  a  prediction  ruler,  time-interval  bell, 
stop  watch,  and  the  necessary  telephones  to  the  post  switchboard, 
mining  casemate,  searchlights,  loading  room,  and  rapid-fire  gun 
batteries.  The  operation  of  the  apparatus  is  similar  to  that  of  the  other 
fire-control  stations.  The  use  of  the  plotting  board  has  been  fully 
expained  under  the  heading  "  Submarine  Plotting  Board." 

The  Mining  Casemate. — This  is  usually  a  substantial  building  either  of 
masonry  or  frame,  one  story  high,  and  about  30  X60  feet  in  dimensions. 
It  is  located  in  such  manner  as  to  protect  it  from  attack  from  the 
land  front  as  well  as  fire  delivered  from  the  entrance  to  the  harbor. 

The  equipment  of  the  mining  casemate  is  necessarily  kept  a  secret. 
Its  purpose,  however,  is  to  explode  the  mines  at  the  proper  instant, 
and  to  control  and  test  them  after  they  are  planted. 

The  Loading  Room. — The  duties  of  the  loading  room  include 
the  mechanical  and  electrical  operations  necessary  for  preparing  the 
mines  for  planting.  Such  operations  are  divided  as  follows : 

1.  Making  turk's-heads: 

(a)  Single-conductor  cable. 
(6)   Multiple  cable. 

2.  Making  telegraph  joints. 

3.  Making  okonite  joints: 

(a)  Uniting  two  single-conductor  cables. 

(6)   Uniting  multiple  cable  and  seven-branch  cables. 

(c)  Uniting  multiple  cable  and  mine  cables. 

(d)  Uniting  mine  cable  to  loading  wire. 

4.  Preparing  compound  plug  for  buoyant  mine. 

5.  Loading  and  testing  compound  plugs. 

6.  Loading  mines. 

7.  Assembling  a  group  of  mines. 

8.  Attaching  mooring  sockets  to  cable. 

(a)  Preparing  mooring  ropes — rule  for  lengths. 

9.  Insulating  exposed  cable  ends. 

The  loading  room  is  in  charge  of  a  non-commissioned  officer  (Chief 
Loader) ,  who  is  selected  for  his  knowledge  of  the  subject.  In  performing 


418 


THE   SERVICE   OF  COAST  ARTILLERY 


his  duties  he  should  keep  the  detachment  busy  at  such  parts  of  the  work 
as  the  several  details  are  best  fitted  to  perform,  exercising  care  that 
no  accident  occurs  from  carelessness  or  neglect;  to  make  the  necessary 
electrical  tests;  to  keep  himself  informed  as  to  the  general  progress  of 
the  work  so  that  no  part  may  fall  behind  and  create  unnecessary  delay ; 
and  finally  to  allow  no  unauthorized  persons  in  the  building. 

Making  a  Turk's-Head. — In  submarine  telegraph  cables  the  armor 
is  jointed  by  a  long  running  splice  with  the  iron  wires,  similar  to  the 
splicing  of  a  rope  to  run  through  a  block.  In  case  of  necessity,  the 
same  device  may  be  employed  in  the  mine  service,  but  the  method  of 
turkVheads  is  greatly  to  be  preferred  when  junction  boxes  are  at  hand 
— and  it  must  be  exclusively  used  in  connecting  the  cable  to  the  mines. 

To  make  a  turk's-head  (Fig.  67  a),  one  private  equipped  with  a  navy 


C 

FIG.  67. 

knife,  cutting  pliers,  hammer,  turk's-head  collar  (large  or  small),  and 
about  14  feet  of  marline  is  required. 

If  the  object  be  to  splice  a  single-conductor  cable,  or  to  unite  a 
multiple  cable  to  several  cables,  the  turk's-head  will  be  made  first;  but 
if  it  be  desired  to  attach  the  cable  to  a  mine  or  mine  buoy,  the  free 
end  will  first  be  passed  through  the  clamping  hole  of  the  mine  cap. 
In  either  case,  the  turk's-head  will  be  made  in  the  following  manner: 

Trim  the  end  square;  at  15  inches  from  it  place  a  wrapping  of  four 
or  five  turns  of  marline  overlapping  each  other  round  the  cable,  and 
finally  secured  by  a  square  knot,  to  form  a  stop  for  the  collar;  slip  on  the 
collar,  flat  side  first  until  it  rests  against  the  stop  of  marline;  unwrap 
the  jute  covering,  and  bend  it  back  regularly  over  the  collar;  do  the 


SUBMARINE   MINES,    SMALL   BOATS,   ETC.  419 

same  with  the  iron  wires  and  the  interior  hemp  serving;  cut  off  the 
iron  wires  with  the  pliers,  removing  about  4  inches  from  one,  and  6 
inches  from  the  next,  alternately;  trim  off  about  4  inches  from  the 
jute  and  hemp  wrapping;  bend  the  iron  wires  separately  to  closely  fit 
the  collar  (making  two  right  angles  with  the  pliers)  and  arrange  the 
ends  smoothly  along  the  cable;  engage  the  end  of  a  strand  of  marline 
under  one  of  the  wires  near  the  collar,  and  wrap  it  regularly  and  closely 
around  the  cable,  until  a  point  about  one  inch  beyond  the  end  of  the 
jute  and  hemp  is  reached;  then,  secure  the  free  end  of  marline  with 
two  half  hitches.  About  12  feet  of  it  are  required.  Where  time  is 
important  the  wrapping  of  marline  may  be  reduced  to  a  couple  of  half 
hitches  (near  collar)  drawn  tight. 

In  case  no  collars  are  at  hand,  a  wrapping  of  marline  of  similar 
form  may  be  substituted. 

If  the  object  be  to  splice  one  cable  to  another,  the  turkVheads  are 
placed  in  their  clamps  in  a  single  junction  box,  the  cores  are  jointed, 
and  the  parts  of  the  junction  box  are  bolted  together,  great  care  being 
observed  not  to  injure  the  exposed  parts  of  the  cores  coiled  inside,  and 
to  see  that  the  wrappings  of  the  turk's-head  are  so  firmly  clamped  that 
no  motion  is  possible. 

If  a  multiple  cable  is  to  be  connected  to  single-conductor  cables,  a 
distribution  box  will  be  used.  The  turkVheads  will  first  be  secured; 
then  the  cores  will  be  united;  lastly,  the  box  will  be  bolted  or  keyed 
together. 

If  the  cable  is  to  be  jointed  to  a  mine  or  mine  buoy,  the  turk's-head 
is  first  drawn  up  until  the  swell  is  in  contact  with  the  cap,  and  the  clamps 
are  then  bolted  fast.  It  is  essential  that  the  clamps  shall  take  a  firm 
hold;  and  if  the  iron  jaws  touch,  it  is  sufficient  proof  that  there  is  not 
enough  marline  wrapping.  Afterwards  the  cores  are  jointed,  and  the 
cap  is  immediately  screwed  to  its  seat.  Care  must  be  taken  to  avoid 
any  unnecessary  bending  or  twisting  of  the  cores,  and  no  pulling  what- 
ever must  be  allowed. 

Telegraph  Joint. — (see  Fig.  676).  The  ends  of  the  wires  to  be 
jointed  are  bared  and  brightened  for  about  1^  inches,  the  bared  ends 
are  laid  across  each  other  at  an  angle  of  about  45  degrees,  the  point  of 
crossing  being  about  one-third  the  distance  from  the  insulation  of 
the  ends.  With  a  pair  of  pliers,  grasp  the  two  wires  firmly  at  the  cross- 
ing; then  wind  closely  and  tightly  the  free  end  of  each  wire  around 
the  short  bared  part  of  the  other,  shifting  the  pliers,  if  necessary,  after 
wrapping  one  end  and  before  beginning  on  the  other,  so  that  the  two 
wrappings  begin  as  close  together  as  possible.  The  two  windings 


420  THE   SERVICE   OF   COAST   ARTILLERY 

should  run  in  opposite  directions.  The  end  of  each  wire  at  the  end  of 
the  wrapping  is  trimmed  or  hammered  down  so  as  to  leave  no  projecting 
sharp  points.  When  completed  in  the  manner  described  the  joint 
should  not  give  in  either  direction.  To  insulate  the  joint  a  piece  of 
rubber  tape,  2  inches  long,  is  cut  from  the  roll,  the  cut  running  in  a 
diagonal  direction  across  the  strip.  Beginning  well  back  on  the  insula- 
tion the  tape  is  applied  under  strong  tension,  each  turn  overlapping 
the  preceding  one  by  about  one-third  of  its  width.  This  winding  is 
continued  forward  and  backward,  sometimes  in  a  straight  and  sometimes 
in  .a  diagonal  direction,  until  the  strip  is  used  up  and  a  substantial 
insulation  is  secured.  The  end  of  the  rubber  tape  is  secured  by  firm 
pressure  continued  for  several  seconds;  a  little  rubber  cement  may 
be  used  to  insure  adhesion.  This  joint  is  used  in  connecting  the  fuses. 

Okoriite  Joint. — This  joint  is  now  prescribed  for  use  in  uniting  all 
conductors  of  cables  placed  under  water  or  exposed  to  dampness. 
The  following  is  prescribed  as  the  method  of  making  the  okonite  joint: 

The  ends  are  bared  and  cleaned,  then  beveled  like  a  sharpened 
lead  pencil  (see  Fig.  67  c),  using  a  very  sharp  navy  knife;  roughen 
the  beveled  part  and  half  an  inch  of  the  insulation  with  the  knife  or  file 
and  wipe  clean  with  gasoline. 

The  wires  may  be  joined  in  three  ways: 

1.  By  using  a  brass  jointer,  in  which  case  about  f  inch  of  the  ends 
of  the  conductor  is  bared;    the  wire  is  secured  by  compressing  the 
longer  diameter.     Smooth  off  any  rough  edges  with  a  file. 

2.  By  a  telegraph  joint,  in  which  case  about  4  inches  of  the  ends 
of  the  conductor  should  be  bared. 

3.  By  the  following  method:    bare  about  4  inches  of  the  ends  of 
the  conductors,  separate  the  wires  of  each  for  about  2  inches,  cut  out 
the  center  wire,  and  spread  out  the  others  radially;  then  put  the  two 
ends  together  as  in  splicing  a  rope,  each  wire  opposite  the  space  between 
two  in  the  other  end;   bend  the  wires  of  one  end  through  the  spaces  of 
the  other  and  wrap  them  closely  and  regularly  around  it;   then  do  the 
same  with  the  other  end.     If  carefully  done,  the  joint  will  be  of  smaller 
diameter  than  the  telegraph  joint. 

In  either  method,  work  the  wrapping  tightly  with  the  pliers  and  be 
careful  to  have  no  protruding  ends.  The  joints,  unless  sleeves  are 
used,  should  show  about  2  inches  of  bare  wire  when  wound.  With 
sleeve  only  a  little  bare  wire  should  show  on  either  end  of  the  sleeve. 
Be  careful  not  to  touch  the  beveled  insulation  with  the  fingers,  and 
handle  the  bare  wire  as  little  as  possible. 

Now  cover  the  bevels  and  joints  with  a  thin  coat  of  okonite  rubber 


SUBMARINE  .MINES,   SMALL  BOATS,   ETC.  421 

cement,  allowing  the  solvent  to  evaporate  thoroughly;  cut  a  two  and  one- 
half  inch  piece  of  okonite  tape  with  diagonal  ends  and,  beginning  at 
the  beveled  insulation,  cover  the  joint  by  applying  the  tape  under  such 
tension  that  its  width  is  about  two-thirds  its  normal  value. 

The  layers  of  tape  should  overlap  and  should  be  stretched  as  applied, 
not  before  beginning  the  joint. 

Repeat  the  above  with  a  piece  of  tape  about  eight  inches  long, 
beginning  well  back  on  the  insulation. 

If  tinfoil  be  on  hand,  cover  with  this  and  then  with  Manson  tape; 
heat  in  the  edge  of  a  torch  or  alcohol  flame,  turning  so  as  to  expose  the 
entire  joint  until  the  Manson  tape  becomes  slightly  pasty;  the  time 
will  be  about  one  minute;  take  off  the  tape  and  tinfoil  and  re-cover 
with  two  layers  of  Manson  tape. 

Gasoline  or  alcohol  on  a  piece  of  waste  answers  well  for  heating 
joints  in  a  boat. 

The  object  of  heating  is  to  convert  the  tape  into  one  compact 
mass  which  offers  the  same  resistance  as  the  original  insulation  of  the 
wire. 

The  joints  may  be  made  without  the  rubber  cement,  but  it  requires 
much  more  care  in  heating  to  get  proper  vulcanization. 

Loading  Mines. — The  mine  cases  are  carried  from  the  storeroom 
to  the  loading  room  on  the  platform  cars  provided,  and  placed  on  the 
loading  skids  with  the  caps  up.  The  caps  are  removed  and  placed 
nearby,  washers,  nuts,  and  keys  being  placed  near  them.  All  screw 
threads  are  then  thoroughly  cleaned  by  use  of  kerosene  and  the  neces- 
sary cleaning  brushes.  The  mine  case  itself  should  be  wiped  out, 
and,  if  it  has  been  in  the  water  previously,  dried  out.  The  explosive 
detail  then  brings  the  explosive  from  the  magazine  to  the  loading  room 
and  it  is  inserted  in  the  mine  case  through  the  loading  hole.  If  dynamite 
is  the  explosive  used,  a  loading  funnel  should  be  placed  in  the  loading 
hole  before  any  of  the  cartridges  are  inserted  in  the  mine  case.  Care 
should  also  be  taken  that  the  cartridges  are  not  broken,  and  that 
canvas  is  placed  on  the  floor  around  and  underneath  the  mine  case. 
Only  one  box  of  explosive  for  each  mine  being  loaded  is  allowed  in  the 
loading  room  at  any  one  time.  When  the  proper  amount  of  explosive 
has  been  placed  in  the  mine  case  the  screw  threads  are  thoroughly 
cleaned  with  button  brushes  and  then  coated  with  rubberine  or  other 
waterproof  material.  The  compound  plugs,  having  been  assembled, 
are  then  screwed  home  with  the  socket  wrench,  a  loading  washer  being 
first  placed  between  the  plug  and  the  mine  case.  Sufficient  force 
should  be  used  in  screwing  the  compound  plug  home  to  insure  making 


422  THE   SERVICE   OF   COAST   ARTILLERY 

the  joint  water-tight.  The  end  of  the  lever  inserted  in  the  openings 
of  the  socket  wrench  should  be  tapped  several  times  with  a  mallet  to 
insure  tightening.  The  mine  cases  are  then  put  in  the  testing  tank, 
and,  if  time  is  available,  allowed  to  remain  there  for  at  least  twenty-four 
hours  before  the  test  is  made  to  determine  whether  the  circuits  have 
been  correctly  made  and  the  joints  made  water-tight.  This  test  can 
either  be  made  by  running  or  by  extending  the  milliammeter  lead 
from  the  mining  casemate  to  the  loading  room  and  taking  a  reading 
of  each  mine,  as  is  done  after  planting;  or,  the  test  may  be  made  by 
using  a  portable  voltmeter  and  four  dry  cells.  The  test  should  show 
the  resistance  of  the  loaded  mine  to  be  between  2,200  and  2,400  ohms. 

Duties  on  the  Water. — Time  will  usually  be  of  the  utmost  importance 
when  a  channel  is  to  be  mined,  and  success  will  very  largely  depend 
upon  the  officer  in  charge  of  the  harbor  mine  defense  in  so  arranging 
the  work  as  to  avoid  delays  and  keep  everyone  constantly  and  actively 
employed.  For  the  work  on  the  water  specially  constructed  boats 
known  as  "mine  planters"  are  fitted  up  for  quickly  placing  the  mines 
in  position.  In  addition  to  a  mine  planter  it  is  necessary  to  have  at 
least  four  small  boats.  One  of  these,  known  as  the  distribution-box 
boat,  is  equipped  with  a  gasoline  engine,  and  should  be  provided  with 
its  own  power  for  hoisting  the  distribution  box  and  at  least  a  500-pound 
anchor.  The  other  three  boats  are  the  ordinary  yawl  boats.  Assuming 
that  a  group  of  mines  has  been  loaded,  assembled  and  placed  on  the 
planting  wharf,  the  duties  on  the  water  would  be  carried  out  in  some 
such  order  as  given  below: 

The  chart  showing  the  approved  scheme  of  mine  defense  is  first 
consulted  and  the  locations  of  the  distribution  boxes  noted.  These 
positions  are  also  marked  on  the  mine  plotting  board.  The  mine 
planter,  with  the  necessary  buoys  and  anchors,  proceeds  to  the  mine 
field,  and  from  some  prearranged  signals  from  the  base-end  stations 
drops  anchors  with  the  keg  buoys  attached  at  the  positions  of  the 
distribution  boxes  as  indicated  on  the  mine  plotting  board.  The  mine 
field  is  next  laid  out. 

It  is  next .  necessary  to  take  soundings  along  the  line  of  mines  in 
order  to  determine  the  lengths  the  mooring  ropes  and  the  lengths  the 
single  conductor  cables  should  be  cut.  If  automatic  anchors  are  used 
such  information  as  may  be  required  about  the  depth  of  water  can 
usually  be  obtained  from  charts,  but  such  information  is  not  sufficiently 
accurate  for  planting  with  the  ordinary  anchors. 

The  soundings  are  made  either  with  the  launch  from  the  mine 
planter  or  the  distribution-box  boat  assisted  by  the  yawl  boats.  The 


OF  THE 

UNIVERSITY 

OF 


SUBMARINE  MINES,   SMALL  BOATS,  ETC.  423 

launch  moves  along  the  line  of  mines  and  takes  soundings  at  the  proper 
intervals,  these  readings  being  recorded  in  a  blank  book  showing  the 
number  of  the  mine  and  the  time  of  day.  It  is  necessary  that  the  tide 
station  be  manned  during  this  time  and  the  operator  in  charge  instructed 
to  keep  a  record  of  the  time  of  day  and  the  tide  readings  taken  at 
least  every  fifteen  minutes. 

The  planter  then  lays  the  multiple  cable  from  the  shore  terminal 
to  the  distribution  box  for  each  group.  The  multiple  cable  is  cut  and 
the  end  passed  to  the  distribution-box  boat,  usually  by  a  heaving  line. 
The  men  in  the  distribution-box  boat  make  a  turk's-head  upon  the  end 
of  the  multiple  cable  and  finally  put  it  in  the  proper  slot  in  the  dis- 
tribution box.  As  a  precautionary  measure  for  recovery  of  the 
distribution  box  should  it  be  pulled  overboard  during  the  operations 
of  planting,  it  is  well  to  buoy  the  multiple  cable  about  100  yards  in 
rear  of  the  distribution  box.  As  soon  as  the  end  of  the  cable  has  been 
put  in  the  slot,  the  conductors  of  the  multiple  cable  are  spread  out 
preparatory  to  identification. 

In  numbering  the  conductors  at  the  mining-casemate  end,  or  shore 
end,  they  are  numbered  clock-wise,  commencing  with  the  marked 
numbers.  At  the  distribution  box  they  are  numbered  contra-clock- 
wise, commencing  with  these  same  numbers,  for  communicating  with 
the  casemate,  the  central  conductor,  is  the  one  to  which  the  boat  tele- 
phone is  attached. 

After  the  ends  have  been  numbered  and  communication  established 
with  the  casemate,  the  casemate  electrician  then  directs  the  distribution- 
box  boat  to  prepare  the  ends  of  the  cable  for  test.  When  this  has  been 
done  word  is  sent  to  the  casemate  electrician,  who  makes  the  prescribed 
test  of  the  cable  to  determine  any  leaks.  The  ends  are  next  tested  to 
determine  if  they  have  been  properly  numbered. 

While  these  operations  have  been  going  on  the  mines  have  been 
taken  aboard  the  planter  and  arranged  for  planting,  as  shown  in 
Plate  XXXVII.  This  is  done  by  the  detail  on  each  side  of  the  planter 
preparing  the  mines  on  its  side  for  planting. 

The  mine  planter  then  moves  out  towards  the  mine  field,  passing 
as  close  to  the  distribution-box  boat  as  precautions  for  safety  will 
permit — passing  it  on  the  starboard;  that  is,  having  the  distribution- 
box  boat  to  port.  The  heaving  line  is  thrown  well  forward  of  the 
distribution-box  boat,  caught  or  picked  up  by  the  party  in  the  boat  and 
secured  at  once  to  a  cleat,  and  after  the  mine  is  dropped  pulled  in  and 
inserted  in  the  proper  slot  for  the  mine  in  question.  A  temporary 
joint  is  then  made  between  it  and  the  proper  conductor  of  the  multiple 


424  THE   SERVICE   OF  COAST  ARTILLERY 

cable  and  the  casemate  electrician  asked  if  the  mine  tests  out  satis- 
factorily. 

If  the  casemate  electrician  informs  the  boat  party  that  the  mine 
tests  all  right  the  joint  is  made  permanent. 

After  the  last  mine  is  planted  the  telephone  is  first  put  on  the  single 
conductor  and  the  casemate  electrician  informed  that  the  boat  party 
is  ready  to  make  a  joint  for  the  last  mine  planted.  When  the  last 
joint  has  been  made  the  distribution  box  is  closed  and  a  buoy  rope, 
attached  to  a  buoy,  is  made  fast  to  its  lid.  The  anchor  of  the  distribu- 
tion-box boat  is  raised  and  the  distribution  box  then  lowered. 


CARE  AND  PRESERVATION  OF  EQUIPMENT 

One  of  the  important  duties  that  the  personnel  of  mine  companies 
are  called  upon  to  perform  is  the  care  and'preservation  of  the  armament, 
material  and  equipment,  comprising  and  pertaining  to  the  mine  defense, 
which  consists  of  the  following: 

At  Fire-Control  Stations. — Position-finding  instruments,  plotting 
boards,  prediction  rulers,  azimuth  instruments,  telephones,  time- 
interval  clock  and  bell,  controller  for  searchlight  and  the  necessary 
charts. 

At  Mining  Casemate. — Storage  battery,  oil  engine,  generator,  power 
panel,  operating  boards,  casemate  transformers,  motor  generators,  and 
telephones. 

At  Loading  Room. — Telephones,  traveling  cranes  and  triplex  block, 
vises,  and  such  tools  and  material  as  may  be  in  the  loading  room  for 
use  or  purposes  of  instruction. 

At  Cable  Tanks. — 19-,  7-,  and  1-conductor  cable,  traveling  cranes, 
triplex  blocks,  and  apparatus  pertaining  to  water  supply. 

At  Boathouse. — Submarine-mine  yawls,  oars,  boathooks,  oar-locks, 
ropes  and  tackle  for  raising  and  lowering  boats. 

At  Storehouse. — Mine  cases,  compound  plugs,  circuit  closers,  anchors, 
anchor  shackles,  mine  shackles,  mooring  sockets,  mooring  cable, 
distribution  boxes,  junction  boxes,  ropes,  small  tools  and  appliances, 
traveling  cranes  and  triplex  blocks. 

Paints  and  oils  should  be  kept  separate  from  other  stores ,  either  in 
different  buildings  or  some  other  convenient  place.  The  floor  where 
such  stores  are  kept  must  be  covered  with  sand  two  or  three  inches 
thick,  and  the  same  renewed  at  intervals.  Kerosene  oil  must  be  kept 
apart  from  other  oils  and  paint. 


SUBMARINE   MINES,   SMALL   BOATS,   ETC.  425 

At  Magazine. — Explosives.  Primers  and  fuses  are  kept  in  a  sep- 
arate room  of  the  magazine  or  some  other  convenient  place. 

At  Searchlight  Shelter.  Searchlight,  rheostat,  switchboard,  tele- 
phone and  necessary  appliances.  If  the  searchlight  does  not  receive 
its  power  from  a  central  plant,  add  generating  set  to  the  above. 

At  Rapid-Fire  Gun  Batteries. — Guns,  carriages  and  necessary 
equipment  and  appliances. 

SUPPLIES,    TOOLS,    ETC.,    AND    THEIR    USE. 

The  supplies  necessary  for  cleaning  mine  material  are:  Kerosene, 
gasoline,  benzene,  alcohol,  pomade,  sandpaper,  emery  cloth,  crocus 
cloth,  and  cotton  waste. 

The  tools  used  in  cleaning  mine  material  are:  steel  scrapers,  wire 
brushes,  paint  brushes,  button  brushes,  chamois  skin,  and  soft  cloth. 

The  supplies  necessary  for  preserving  mine  material  are:  cosmic- 
dense,  white  and  red  lead,  beef  tallow,  varnish,  raw  linseed  oil,  lard  oil, 
and  sperm  oil. 

Cosmic-dense  is  applied  to  bright  parts  of  oil  engines,  generators, 
and  motor-generators,  when  out  of  commission.  It  is  also  applied  to 
brass  screw  threads,  parts  of  triplex  blocks  and  trolley  systems,  as  well 
as  to  all  tools  that  are  liable  to  rust.  It  should  be  renewed  three  times 
a  year. 

White  lead  is  used  for  painting  mines,  and  in  lead  tallow  mix- 
ture. 

Red  lead  is  used  for  the  first  coat  on  mines  when  taken  from  the 
water  and  after  rust  has  been  removed;  also  for  first  coat  on  oil  engines. 
The  mixture  for  first  coat  consists  of  100  pounds  red  lead  to  5  gallons 
raw  linseed  oil.  One  gallon  of  paint  to  each  ten  mines. 

Beef  tallow  (rendered)  is  used  in  white  lead-tallow  mixture  for 
smearing  the  screw  threads  of  mine  cases,  steel  screw  threads  of  com- 
pound plugs,  bolts,  nuts,  washers,  and  all  surfaces  of  flat  joints.  The 
mixture  consists  of  one  part  white  lead,  to  four  parts  beef  tallow.  The 
mixture  is  melted  and  applied  to  surfaces  while  hot. 

Raw  linseed  oil  is  used  in  paint  mixtures.  For  priming  coat: 
o  gallons  to  each  100  pounds  of  red  ,lead.  For  painting  mine  cases 
neutral  gray;  2^-  gallons  to  each  '100  pounds  white  lead,  2J  gallons 
turpentine,  1  gallon  liquid  dryer,  and  1  pound  lampblack. 

Asphaltum  varnish  is  used  for  painting  anchors,  distribution  boxes, 
fuse  cans  and  plug  proper  of  compound  plugs,  junction  boxes,  shackles, 
sister  hooks,  and  iron  work  of  operating  boards  and  power  panels. 


426  THE   SERVICE   OF  COAST  ARTILLERY 

Lard  oil  is  used  for  preserving  copper  or  brass  parts  and  screw 
threads. 

Sperm  oil  is  used  on  the  iron  and  steel  work  of  electrical  instruments, 
and  on  tools  to  keep  them  free  from  rust. 

No  oil  should  be  used  on  electrical  contacts. 

Care  of  the  Storage  Battery. — Take  daily  readings  of  the  pilot  cell, 
making  record  of  specific  gravity,  voltage,  and  temperature  of  the 
cell.  See  that  the  battery  is  given  regular  weekly  charge  at  normal 
rate.  Examine  the  plates  with  battery  lamp  for  sulphate  (white 
deposit  on  the  negative  plate) ,  buckling,  blistering,  or  anything  unusual 
in  their  appearance.  Always  keep  electroylite  at  proper  height  in 
each  cell  (one-half  inch  from  top).  Comply  carefully  with  the  special 
instructions  issued  regarding  the  care  of  the  storage  battery. 

Care  of  Dynamos  and  Motor  Generators. — See  that  all  surfaces  are 
free  from  rust,  dust  or  dirt.  See  that  oil  holes  or  oilers  are  kept  filled; 
that  all  connections  are  tight;  that  there  are  no  loose  nuts  or  contacts; 
that  brushes  are  in  good  condition,  i.e.,  bear  evenly  and  are  not  chipped 
or  covered  with  foreign  material;  that  when  brushes  are  worn  they  are 
replaced  in  due  time  with  new  ones. 

The  commutator  should  be  smooth,  free  from  grit,  and  clean 
throughout;  slight  inequalities  should  be  removed  by  running  the 
generator  with  the  brushes  off  and  allowing  a  block  of  wood  properly 
beveled  and  covered  with  very  fine  sandpaper  (not  emery  paper)  to 
bear  evenly  on  the  rough  surface.  The  machine  should  be  protected 
with  rubber  or  canvas  paulins  whenever  possible. 

Care  of  Power  Panels  or  Operating  Boards. — All  connections  should 
be  examined  to  see  that  they  are  tight,  contacts  and  switches  clean,  dry, 
and  free  from  dust,  oil  or  gum  of  any  description.  Switches  adjusted 
so  that  they  are  not  loose  nor  wabbly;  when  thrown  they  should  make 
or  break  the  circuit  evenly  and  without  unnecessary  sparking.  No 
verdigris  should  be  allowed  anywhere. 

Care  of  Electric  Lights. — Lights  should  be  kept  clean  at  all  times. 
Switches  should  not  be  permitted  to  spark  badly  without  being  replaced. 
Burnt-out  or  dim  lamps  should  be  replaced  immediately.  An  extra 
supply  of  fuses  should  be  on  hand  to  replace  any  that  may  be  blown 
out.  Only  fuses  or  fuse  wire  should  be  used  for  this  purpose. 

Care  of  the  Oil  Engine. — All  bearings  should  be  kept  smooth  and  well 
lubricated.  Oil  cups  kept  constantly  filled. 

Before  the  engine  is  started  care  should  be  taken  to  see  that  the 
water  tank  is  clean  and  free  from  mud  or  sediment,  and  that  it  is  full 
of  clean  water,  the  water  to  be  above  level  of  top  pipe.  Oil  tank  full 


SUBMARINE  MINES,  SMALL  BOATS,   ETC.  427 

of  kerosene  oil.  Under  no  circumstances  should  gasoline  oil  be  used 
in  the  engine.  Before  starting  see  that  the  two  cocks  which  supply 
water  to  the  vaporizer  valve  box  water  jacket  are  fully  open;  also 
the  cock  on  main  water  pipe  from  bottom  of  the  tank.  The  spray  nozzle 
and  vaporizer  must  be  kept  free  from  carbon.  The  piston  must  be 
clean  and  well  oiled;  the  khotal  lamps  clean,  free  from  soot  and  always 
filled.  A  small  bottle  of  wood  alcohol  should  be  at  hand  for  starting 
up  lamps,  also  asbestos  wicks  in  cups  under  burners. 

In  frosty  weather  the  water  must  be  drained  out  of  the  cooling  tank, 
circulating  pipes  and  water  jacket,  in  order  to  prevent  damage  from 
freezing. 

Care  of  Machinery  Being  Placed  Out  of  Commission. — All  bearing 
surfaces  are  carefully  cleaned  and  covered  with  white  lead  and  lard  oil 
(white  tallow  mixture) ;  all  small  loose  parts  are  removed,  covered  with 
cosmic,  wrapped  in  burlap  and  put  in  a  small  box,  when  practicable. 
The  box  should  be  plainly  marked  and  stored  under  cover.  The  machine 
if  not  already  under  cover  should  be  housed  or  protected  in  some  way. 

Storage  of  Mines. — Mines  should  be  cleaned  and  painted,  the  screw 
threads  covered  with  the  lead-tallow  mixture  and  the  holes  fitted  with 
wooden  plugs  which  have  been  thoroughly  greased.  They  are  then 
stored  on  racks  or  skids  in  the  storeroom.  Mine  cases  should  not  be 
stored  in  contact  with  each  other  where  it  can  be  avoided. 

Small  Boats. — A  small  boat  may  be  defined  as  any  small  open 
vessel  moved  by  oars.  Those  used  in  connection  with  submarine  mine 
work  may  be  either  cutters,  gigs  or  yawls,  usually  the  latter. 

The  curved  piece  of  timber  to  which  the  sides  of  a  boat  are  united 
in  the  fore  end  is  called  the  stem.  The  bending  or  rounded  part  forward 
is  called  the  bow  or  prow.  The  middle  portion  is  called  amidships.  The 
after  or  rear  end  is  called  the  stern.  Fore  implies  the  portion  forward; 
aft  or  abaft  means  toward  the  stern.  The  longitudinal  timber,  or  series 
of  timber  scarfed  together,  extending  from  stem  to  stern  along  the 
bottom  is  called  the  keel.  That  part  of  the  bottom  which  is  broadest 
and  most  nearly  flat  is  called  the  bilge.  The  width  of  a  boat  is  expressed 
as  the  beam. 

When  the  boats  are  constructed  of  planks  running  fore-and-aft, 
their  edges  meeting  but  not  overlapping,  they  are  called  carvel-built. 
When  the  planks  run  fore-and-aft  and  their  edges  overlap,  they  are 
called  clinker-built.  When  the  planks  run  in  a  diagonally  opposite 
direction  from  the  outside  layer,  they  are  called  diagonal-built.  The 
seats  on  which  the  crew  sit  are  called  thwarts.  When  two  men  pull  on 
one  oar  it  is  said  to  be  double-banked.  Boats  are  called  single-  or  double- 


428  THE   SERVICE   OF   COAST   ARTILLERY 

banked,  if  they  have  one  or  two  men  to  a  thwart.  The  space  abaft  the 
after  thwart  is  called  the  stern-sheets. 

The  notches  for  the  oars  are  called  rowlocks',  if  wooden  pins  are  set 
in  the  rails  they  are  called  thole-pins;  if  metal  forks  or  stirrups  are  used 
they  are  called  oarlocks.  Purchases  made  with  two  blocks  and  a  length 
of  rope  (used  for  hoisting  boats)  are  called  boat-falls.  A  line  made  fast 
to  a  ring-bolt  in  the  stem  is  called  the  painter. 

The  upper  rail  of  a  boat  is  called  the  gunwale.  The  piece  of  wood  or 
metal  filling  across  the  head  of  a  boat's  rudder  is  called  the  yoke;  lines 
attached  to  it  are  called  yoke-lines.  The  bottom  boards  of  a  boat  are 
called  floorings  or  gratings.  A  small  keg  used  for  carrying  fresh  water 
is  called  a  boat-breaker. 

The  signal  used  to  order  boats  to  return  is  called  boat-recall. 

Boat  Drill. — The  small-boat  detachments  place  in  their  respective 
boats  the  necessary  oars,  oarlocks,  life  preservers,  buckets,  and  heaving 
lines. 

The  men  are  numbered  in  each  detachment  as  follows: 

Nos.  1-3-5  on  starboard  oars,  No.  1  on  bow  oar; 
Nos.  2-4-6  on  port  oars,  No.  2  on  bow  oar; 
No.  7  in  bow  to  man  boathook  or  heaving  line. 
Non-commissioned  officer  at  rudder. 

No.  1  enters  boat  and  makes  ready  to  cast  off  bridles  when  boat  is 
lowered.  All  being  in  readiness,  the  boats  are  lowered  at  once  by 
the  remaining  members  of  the  crew  at  the  command:  Lower. 

When  the  bridles  have  been  cast  off,  the  No.  1  of  each  boat  mans  the 
boathook,  and  holds  boat  alongside  the  ladder  until  the  remaining 
members  of  the  crew  take  their  seats. 

Shove  Off. — At  this  command,  No.  7,  the  bowman,  shoves  the  boat 
clear,  being  eareful  to  clear  the  piling  in  leaving  the  boathouse  or 
mooring. 

Up  Oars. — The  crew  simultaneously  seize  and  raise  their  oars  to 
the  vertical  position.  The  oars  being  held  directly  in  front  of  them, 
the  blades  fore-and-aft,  and  the  handles  clear  of  the  bottom  of  the 
boat.  The  oars  are  held  by  hoth  hands. 

Let  Fall. — The  oars  are  lowered  quickly  into  the  oarlocks,  brought 
level  with  gunwale,  blades  brought  horizontal,  and  all  trimmed  on 
the  aft  oars. 

1.  Give  Way  Together.  2.  Give  Way. — At  the  first  command,  the 
men  reach  well  forward,  blades  nearly  vertical,  and  get  ready  for  the 
stroke.  At  the  second  command  they  dip  their  oars  at  the  same 


SUBMARINE   MINES,   SMALL  BOATS,   ETC.  429 

time  as  the  stroke  oar,  and  commence  rowing,  keeping  stroke  with  the 
men  directly  in  front  of  them,  and  all  lifting  their  blades  to  the  height  of 
the  gunwale  on  the  return.  Oars  must  not  splash  under  any  con- 
sideration. 

In  Bows. — In  case  no  extra  man  is  in  the  bow  to  man  the  boat- 
hook,  this  command  is  given  when  making  a  landing  alongside  of  a 
vessel,  or  a  wharf.  The  bow  oarsmen  finish  their  stroke,  then  "  toss  " 
their  oars  into  the  boat,  and  lay  them  with  blade  to  the  bow.  No.  1 
then  takes  the  boat  hook  and  stands  ready  to  fend  off  and  hold  the 
landing.  When  the  boat  has  sufficient  headway  to  carry  it  properly 
to  the  landing,  the  command  is  given. 

Way  Enough. — This  command  is  given  while  the  oars  are  in  the 
water;  the  stroke  is  finished,  and  the  men  toss  their  oars  all  together, 
and  lay  them  in  the  boat.  The  oars  are  put  next  to  the  rail,  blades 
towards  the  bow.  The  oarsmen  remain  seated  until  given  further 
command. 

1.  Stand  by  to  lay  on  oars.  2.  Oars. — This  command  is  given  if  it  is 
desired  to  stop  rowing  temporarily.  At  the  second  command,  given 
while  the  oars  are  in  the  water,  they  finish  their  stroke,  and  bring  their 
oars  level  with  the  gunwale,  blades  horizontal,  trimmed  on  after 
oars. 

1.  Trail.  2.  Oars. — This  command  is  used  in  passing  under  bridges 
or  wharfs  where  the  room  is  insufficient  to  toss  oars.  The  second 
command  is  given  while  the  oars  are  in  the  water;  the  stroke  is  finished, 
the  oars  thrown  out  of  the  oarlocks,  and  are  allowed  to  trail  astern. 
To  bring  the  oars  back  inboard  the  command:  Oars,  is  given. 

1.  Give  Way,  Starboard',  Back-port.  2.  Give  Way. — This  command 
is  used  to  turn  the  boat  short  around  to  the  port. 

1.  Give  Way,  Port,  Back-starboard.  2.  Give  Way. — Same  as  pre- 
ceding command,  to  turn  the  boat  to  starboard. 

After  either  command,  when  the  boat  has  the  desired  direction,  the 
command  is  given:  1.  Give  way  together.  2.  Give  way. 

Hold  Water. — This  command  is  given  when  it  is  desired  to  stop 
the  boat's  headway.  The  blades  of  the  oars  are  held  vertically  in  the 
water.  To  resume  rowing  the  command:  Oars,  is  given  and  the  crew 
takes  the  position  given  under  the  command:  Let  fall. 

Stern  All. — This  command  is  given  when  it  is  desired  to  move  the 
boat  astern.  The  crew  back  water,  keeping  stroke  as  in  the  regular 
way.  To  resume  rowing  in  the  regular  direction,  the  command:  Oars,  is 
given. 

1.  Stand  by  to  Toss.     2.   Toss. — This  command  is  given  near  the 


430  THE  SERVICE   OF  COAST   ARTILLERY 

end  of  a  stroke.     The  oars  are  raised  quickly  to  the  vertical  position 
as  in  up  oars. 

If  it  is  desired  to  put  the  oars  in  the  boat,  the  command:  Boat, 
Oars,  is  given,  at  which  the  oars  are  lowered  towards  the  bow,  and  laid 
in  the  boat  as  previously  described. 


CHAPTER  X 
SEACOAST  ENGINEERING 

SE  AGO  AST  engineering  may  be  divided  into  two  general  classes. 
The  first  comprehends  the  location,  arrangement  and  construction  of 
emplacements  for  seacoast  armament;  while  the  second  appertains  to 
the:  (1)  Location  and  measurement  of  horizontal  base  lines.  (2)  Tri- 
angulation  in  connection  with  the  location  of  horizontal  base  lines,  gun 
centers,  and  directing  points  of  batteries.  (3)  The  determination  of 
the  true  azimuth.  (4)  The  location  of  pintle  centers,  and  orientation 
of  gun  and  mortar  azimuth  circles.  (5)  Leveling.  (6)  Principles  of 
hydrographic  surveying. 

The  first  division  is  a  function  of  the  National  Defense  Board  and 
the  Corps  of  Engineers.  In  this  connection  fortifications  are  situated 
so  as  to  be  a  reasonable  strategic  distance  outside  or  in  front  of  the 
point  to  be  defended,  with  a  view  to  preventing  the  ships  of  the  enemy 
from  lying  within  effective  bombarding  range  of  such  points  without 
being  liable  to  injury  from  the  armament  of  such  fortifications. 

Consideration  is  given  to  the  location  of  gun  batteries:  (1)  With  a 
view  to  their  efficiency  under  conditions  described  above.  (2)  With  a 
view  of  compelling  the  enemy  to  pass  them  in  a  clear  waterway.  (3) 
With  a  view  of  restricting  the  front  of  the  enemy,  if  practicable,  and  at 
the  same  time  have  a  convergent  fire  upon  him.  (4)  With  a  view  of 
having  the  batteries  at  such  a  distance  apart  as  to  prevent  the  con- 
centration of  the  enemy's  fire  upon  them  and  still  allow  for  mutual 
support.  (5)  With  a  view  of  not  masking  or  limiting  the  field  of  each 
other's  fire  and  at  the  same  time  not  permitting  the  enemy's  fire  to 
enfilade  nor  take  them  in  reverse.  (6)  With  a  view  to  the  protection 
of  their  flanks  and  rear  so  that  they  cannot  be  cut  off  by  small  landing 
parties.  (7)  With  a  view  to  their  concealment,  so  that  their  location, 
height,  and  azimuth  will  not  be  discovered  by  the  assailants. 

Consideration  is  given  to  the  location  of  mortar  batteries:  (1)  With 
a  view  to  their  command  of  dead  angles  which  cannot  be  reached  by 
rifle  fire.  (2)  With  a  view,  if  practicable,  of  placing  the  channel  in  a 

431 


432  THE  SERVICE  OF  COAST  ARTILLERY 

single  zone.     (3)  With  a  view,  if  practicable,  of  covering  all  anchorages 
in  the  inner  harbor. 

All  landing  points  are,  when  practicable,  covered  by  rapid-fire  guns. 


BASE    LINES,    ETC. 

Location  and  Measurement  of  Horizontal  Base  Lines. — In  determin- 
ing the  location  of  a  horizontal  base  line  the  following  conditions  should 
be  fulfilled  as  far  as  practicable.  (1)  Its  length  should  be  as  long  as 
possible  and  2,000  yards  when  practicable.  (2)  An  uninterrupted  view 
of  the  whole  field  of  fire,  or  that  portion  of  the  field  of  fire  which  the  base 
line  is  to  serve,  should  be  obtainable.  (3)  Both  base  ends  should  be 
in  such  position  that  they  will  not  be  exposed  unnecessarily  to  the 
fire  of  attacking  vessels.  (4)  Both  base  ends  should  be  readily  access- 
ible and  the  stations  located  so  that  they  are  invisible  from  the  field 
of  fire.  (5)  Base  lines  crossing  water  areas  should  be  so  located  that 
the  communication  cables  can  be  protected  from  raiding  parties  and 
are  not  unnecessarily  exposed  to  anchorage  areas.  (6)  The  direction, 
length  and  general  location  of  a  base  line  should  be  such  that  the  lines 
of  sight  converging  from  its  ends  upon  the  target  at  different  parts  of 
the  field  of  fire  shall  intersect  at  favorable  angles,  and  thus  furnish 
ranges  and  azimuths  to  the  guns  with  a  minimum  of  error.  (7)  The 
base  ends  should  be  so  located  that  observation  from  the  stations  will 
not  be  interfered  with  by  smoke  from  the  batteries. 

After  the  location  of  the  base  line  has  been  agreed  upon  the  first 
step  is  to  mark  the  base  ends,  which  is  ordinarily  done  by  sinking  a  stone 
post  in  the  earth  two  or  three  feet  and  extending  a  few  inches  above 
the  surface  of  the  ground  and  by  indicating  on  the  top  of  such  post  a 
center.  This  is  usually  done  by  drilling  a  quarter  or  half  inch  hole  in 
the  stone  and  putting  in  a  copper  plug,  the  center  of  the  copper  plug 
being  marked  by  the  intersection  of  two  of  its  diameters. 

The  actual  measurement  of  a  base  line  is  made  with  steel  tapes 
usually  of  one-hundred  foot  lengths.  A  sufficient  number  of  marking 
stakes  should  be  erected  between  the  two  ends  of  the  base  line  before 
the  measuring  commences.  These  consist  of  pieces  of  scantling  about 
3  or  4  inches  in  cross  section  or  even  less,  sharpened  at  one  end,  and 
sufficiently  long  to  project  about  one  and  one-half  feet  above  the 
surface  when  driven  firmly  in  the  earth.  The  upper  end  should  be 
capped  with  a  strip  of  zinc  or  tin.  The  stakes  are  aligned  from  the 
initial  point  by  setting  a  transit  up,  sighting  on  the  opposite  end  of  the 


SEACOAST  ENGINEERING  433 

base  line  and  then  clamping  the  instrument  in  the  direction  of  the  pro- 
posed line.  The  marking  stakes  are  then  brought  into  line  and  driven 
to  approximately  the  same  level.  The  height  of  the  upper  surface  of 
each  stake  above  the  assumed  datum  level  should  be  determined  by 
using  the  Y  level  and  leveling  rod. 

The  accuracy  required  for  base  lines  used  in  artillery  work  is  taken 
as  1  in  50,000,  that  is,  a  permissible  error  of  one  foot  in  50,000  feet.  In 
order  to  obtain  this  degree  of  accuracy  the  temperature  of  the  tape 
at  the  time  of  measurement,  to  the  nearest  degree,  must  be  taken;  the 
slope  determined  by  stretching  over  stakes  whose  elevation  above  a 
given  datum  are  known,  and  the  pull  on  the  tape  measured  by  spring 
balances.  The  work  should  be  done  in  cloudy  weather  and  with  little 
wind. 

The  actual  measurement  of  the  base  line  is  conducted  as  follows: 
The  tape  is  stretched  over  two  stakes  by  two  assistants,  one  in  rear  of 
the  rear  stake  and  one  in  front  of  the  forward  stake.  The  spring 
balance  is  attached  at  the  forward  end,  and  in  stretching  care  must  be 
taken  not  to  bring  a  strain  on  either  stake.  The  rear  end  graduation 
is  made  to  coincide  exactly  with  the  initial  point  or  a  scratch  on  the 
zinc  cap  of  the  marking  stake  which  indicates  the  forward  end  of  the 
previous  tape  length.  A  pull  of  from  10  to  15  pounds  is  applied  and 
when  the  tape  is  sufficiently  stretched  the  forward  end  is  marked. 
The  thermometer  should  be  carried  about  the  height  of  the  tape 
when  stretched  and  in  such  position  as  not  to  be  affected  by  the  heat 
of  the  body.  A  reading  should  be  taken  as  each  stake  is  marked.  The 
process  is  repeated  from  one  marking  stake  to  the  other  until  the  end 
of  the  base  line  is  reached.  An  accurate  record  of  the  data  should  be 
made.  The  tape  should  never  be  dragged  on  the  ground  on  account 
of  possible  injury  thereto  and  the  variation  which  would  be  caused  in 
the  temperature  of  the  same.  The  line  should  be  measured  at  least 
twice  and  any  discrepancy  at  the  last  stake  being  measured  by  a  finely 
graduated  scale. 

For  the  accuracy  desired  in  artillery  base  lines  the  tape  should 
not  be  stretched  by  hand,  as  it  is  impossible  to  hold  the  tape  graduation 
steady  at  a  given  point  or  to  apply  a  steady  pull.  Any  device  which 
can  be  placed  firmly  in  position  and  which  involves  the  principle  of  the 
lever  or  the  screw  should  be  used  to  get  a  steady  pull  on  the  tape. 

The  base  line  having  been  found  to  consist  of  a  certain  number 
of  tape  lengths,  it  is  necessary  to  know  the  horizontal  distances  between 
the  ends  of  tape  lengths  before  the  length  of  the  base  line  can  be 
calculated.  These  will  differ  among  themselves  on  account  of  the 


434  THE  SERVICE  OF  COAST  ARTILLERY 

difference  in  slope,  temperature,  etc.  It  is,  therefore,  necessary  to  know 
the  distance  between  the  end  marks  of  the  tape  under  one  set  of 
conditions  as  to  temperature,  tension  and  sag,  in  order  that  its  length 
under  any  other  conditions  may  be  calculated. 

If  these  data  cannot  be  obtained  from  the  maker,  recourse  may  be 
had  to  the  National  Bureau  of  Standards,  Treasury  Department,  where 
the  determination  for  tapes  up  to  300  feet  in  length  is  made  free  of 
charge.  This  information  will  usually  be  given  in  the  following  form: 
Its  graduated  length,  say  75  feet,  is  the  true  distance  between  its  end 
graduations  when  the  tape  is  subjected  to  a  certain  stated  pull  (P), 
at  a  certain  stated  temperature  (T),  and  when  supported  at  points  a 
certain  stated  distance  (/))  apart.  If  the  tape  is  supported  throughout 
its  entire  length  as  when  lying  on  a  level  surface,  d0  =0. 

These  are  called  standard  conditions,  and  will  usually  differ  in  one 
or  more  particulars  from  those  actually  existing  or  employed  at  the 
time  the  base  line  is  measured.  Each  measured  tape  length  therefore 
must  receive  corrections  in  order  to  obtain  its  actual  length  under  the 
actual  conditions.  The  number  of  these  corrections  are  in  general  as 
follows:  Correction  of  slope  or  difference  of  level;  correction  for  temper- 
ature; correction  for  sag  and  correction  for  pull  or  stretch  of  metal. 

It  is  thought  that  a  clearer  understanding  of  the  method  of  making 
these  corrections  will  be  obtained  by  taking  the  following  example : 


DATA   FOR   STEEL   TAPE 

Horizontal  distance  between  its  end  graduations  is  75  feet  =  900" 
when  the  tape  is  at  62°  F. ;  pull  10  Ibs. ;  and  when  supported  at  its 
middle  point  (d0  =  450"). 

0  =  0.0562;  log  0  =  4.79239-10; 

E  =  28,200,000 ;  log  E  =  7.45025 ; 

TF  =  0.0368  Ibs.;  \ogW  =  6.83251-  10; 

£  =  0.0024  sq.in.  log  S  =  7.38021-  10. 

PROBLEM 

Measuring  "  base  line,"  making  all  necessary  corrections,  i.e.,  slope, 
temperature,  sag  and  pull. 

The  following  instruments  and  accessories  are  used  in  the  field 
work: 


SEACOAST  ENGINEERING 


435 


Transit  and  tripod  (complete). 

Y  level      "       " 

Leveling-rod. 

75  ft.  steel  tape. 

Spring  balances. 

Devices  for  applying  pull  on  tape  (front  and  rear), 

Stakes  (2"X4",  zinc-capped)  (6)  . 

Malls  (2). 

Thermometer  (1). 

Penknife  (to  mark  on  zinc  cap)  . 

DATA 
L  =75  ft.  =  900" 


P=13  Ibs. 


Levels. 

1.  3.478' 

2.  3.264' 

3.  3.785' 

4.  3.795' 

5.  3.104' 

6.  3.098' 


1.  CORRECTION  FOR  SLOPE: 

3.478' 
3.264' 

0.214'  =  2.568"  =  hi. 

3.795' 

3.785' 


Temperatures. 
84°     1st  tape  length 
82°     2d      "         " 
86°     3d      "         " 
86°     4th     "         " 
87°     5th     " 


5)425C 


85°  =  mean  temperature. 


3.785' 
3.264' 

0.521'  =  6.252"  =  h2. 

3.795' 

3.104' 


0.691'  =  8.292 


3.104' 
3.098' 

0.006'  =  .072"  =  h5. 

log    2.568"=   .4095950 
2 


log  (2.568)2=   .8181900  =  6.59462  =  hl2. 


436  THE  SERVICE  OF  COAST  ARTILLERY 

log    6.252"=   .796019 
2 


log  (6.252)2=  1.592038  =  39.088  =  /i22 
h32=  (.120)2=   .0144 
log    8.292   =:   .9186593 
2 

log  (8.292)2  =  1.8373186  =  68.7573  =  h 
/i52=  (.072)2=   .005184 


/H2=     6.59462 
h22=  39.08800 

fc32  =       .01440 

/i42  =   68.75730 
h52=       .005184 

C1 

"  2/i 

-  ~  -063588 


2/i2=114.459504nr/ 

2.  Correction  for  Temperature: 

Ct  =  a(rw-770 
=  +0.6417/r. 

3.  Correction  for  Sag: 


c'=lr(iSS)2((13)2x(450)2"(900)2(10)2); 


log  900  =  2.9542425 
6.8325089 


,2 

log.  000682 

log  46,777,500  =  7.6700370w 

4.2892973^ 
log  (24X16900)  =5.6080979 

log  Cs  =  8.6811994w     .-,  Cs=  -  .047995". 
Total  Cs=  -.047995"  X5  =  0.239975". 


SEACOAST   ENGINEERING  437 

4.  Correction  for  Pull. 

(P-P0)L_       (13-10)900       ^  2700 
p~       ES       ~  28,200,000  X.  0024  "67680 
=  (7P=+ 0.03989. 

Total  Cp=  +  0.03989 X 5  =  .19945" 

SUMMARY  OF  CORRECTIONS 

Ci=  -0.063588"  Ct=  +0.64170" 

Cs  =  -  0.239975"  Cp  =  +  0. 19945" 

-0.303563"  +0.84115" 

-0.303563" 

+  0.537587" 

Standard  length  of  tape  =  900". 

900"  X    5"  =  4500"       =  length  of  base  line  under  standard  conditions. 
4500" +  .54"  =  4500. 54"==  length  of  base  line  under  local  conditions  at 

time  of  measurement. 
In  feet  =  375.0448'. 

Triangulation  in  Connection  with  the  Location  of  Horizontal  Base 
Lines,  Gun  Centers,  and  Directing  Points  of  Batteries. — The  triangula- 
tion  stations  should,  when  practicable,  be  located  so  that  the  angles 
will  each  be  greater  than  30  degrees  and  less  than  120  degrees.  The 
transit  (see  Plate  XXIV)  should  have  at  least  two  verniers  and  the 
least  count  should  not  be  greater  than  20  seconds.  The  plate  of  the 
ordinary  engineers  transit  given  shows  in  detail  its  principal  parts. 

Before  using  the  instrument  it  should  be  put  in  thorough  adjustment, 
as  every  transit  is  liable  to  and  in  general  possesses  errors  of  both 
eccentricity  and  graduation.  If  the  center  of  motion  of  the  vernier 
plate  does  not  coincide  accurately  with  the  center  of  the  graduated 
plate,  then  as  the  limb  is  turned,  the  vernier  will  have  an  eccentric 
motion  with  reference  to  the  limb  manifestly  resulting  in  errors  of 
measurement.  In  order  to  eliminate  these  errors  two  verniers  are 
used  whose  zeros  are  as  nearly  180  degrees  apart  as  possible,  or  three 
120  degrees  apart.  The  mean  of  the  readings  of  these  verniers  is 
free  from  errors  of  eccentricity.  An  eccentricity  of  centers  of  1-1000 
inch  would  cause  a  maximum  error  of  I'  08"  on  a  six-inch  limb  with  but 
one  vernier.  It  is  not  unusual  for  an  instrument  to  have  an  eccentricity 
of  several  times  this  amount. 

Errors  of  graduation  are  in  the  main  periodic  in  character,  and  are 


438  THE  SERVICE  OF  COAST  ARTILLERY 

due  to  errors  in  the  dividing  engine  in  which  the  circles  are  graduated. 
The  result  is  a  progressive  closing  of  the  intervals  between  successive 
graduations  in  certain  portions  of  the  limb,  followed  by  a  corresponding 
extension.  Such  errors  are  eliminated  or  minimized  by  reading  each 
angle  on  several  different  portions  of  the  limb — a  process  which  is 
shortened  by  the  use  of  two  or  three  verniers. 

Accidental  errors,  as  they  are  called,  must  also  be  eliminated  as  far 
as  possible.  Such  errors  are  brought  to  light  in  subsequent  measure- 
ments of  an  angle  on  the  same  part  of  the  limb  of  an  instrument  with 
fine  readings  giving  discordant  results.  They  are  due  to  many  and  often 
unknown  causes — such  as  the  difficulty  of  exactly  duplicating  a  setting 
of  the  transit  on  a  given  signal  pole  or  target — and  are  sought  to  be 
eliminated  by  making  more  than  one  reading  of  the  angle  on  each  of 
the  selected  portions  of  the  limb. 

The  errors  just  mentioned  are  errors  found  on  the  most  perfectly 
adjusted  instrument.  The  following  adjustments  must  be  carefully 
made,  frequently  tested  and  rectified: 

The  adjustment  of  the  plate  levels  especially  must  be  carefully  made. 
These  levels  indicate  when  the  vertical  axis  of  the  instrument  is  truly 
vertical.  If  this  is  not  so,  then  the  telescope  when  turned  upon  its 
trunnions  will  not  move  in  a  vertical  plane,  and  hence  the  horizontal 
angle  between  two  distant  stations  at  different  altitudes  will  not  be 
correctly  measured.  When  the  telescope  is  provided  with  an  attached 
level  we  have  a  very  accurate  means  of  testing  or  rectifying  errors  of 
this  kind. 

Even  when  the  axis  is  truly  vertical  the  two  standards  may  be  of 
different  lengths  due  to  lack  of  perfect  adjustment,  unequal  expansion 
or  contraction,  etc.,  thus  causing  the  telescope  to  again  revolve  in  an 
oblique  plane,  and  introduce  errors  similar  to  those  just  referred  to. 
Unlike  the  last,  however,  these  errors  may  be  eliminated  by  reading 
the  same  angle  an  equal  number  of  'times  with  telescope  direct  and  then 
telescope  inverted.  To  measure  an  angle  with  telescope  inverted, 
"  tumble"  or  "transit"  the  telescope,  leaving  the  trunnions  in  the  same 
beds,  and  then  turn  the  vernier  plate  180  degrees,  or  until  the  telescope 
points  to  one  of  the  stations. 

The  adopted  methods  of  reading  angles  in  triangulation  work  for 
coast  artillery  is  that  known  as  the  "  repeating  method."  By  this 
method  the  limb  is  clamped  in  any  position  and  left  undisturbed  while 
pointings  are  made  to  all  visible  stations  in  succession  around  the 
horizon,  and  both  verniers  read  for  each  pointing.  Angles  are  then 
found  by  taking  the  difference  between  the  proper  mean  reading. 


SEACOAST  ENGINEERING  439 

More  in  detail,  the  method  is  as  follows:  Suppose  a  transit  be  set 
up  over  the  station  marked  at  B  (Fig.  68),  and  accurately  leveled. 
Clamp  the  vernier  plate  a  little  in  advance  and  approximately  at  zero, 
but  without  reference  to  any  particular  setting.  Turn  the  telescope  on 
signal  at  the  station  A ,  clamp  the  limb  and  do  not  unclamp  it  until  the 
set  of  readings  about  to  be  described  is  completed.  Secure  accurate 
bisection  of  the  signal  by  the  vernier  tangent  screw.  Read  and  record 
both  verniers.  Unclamp  the  vernier, 
point  and  read  in  the  same  manner 
on  D  and  then  on  C.  After  record- 
ing the  last  reading  see  if  the  signal 
remains  accurately  bisected.  If  not, 
perfect  the  bisection,  record  the  new 
reading,  and  from  this  signal  as  a  start- 
ing point,  proceed  around  to  the  left, 
sighting  on  the  signals  successively  as 
before,  but  in  inversed  order.  These 
pointings  should  be  entered  in  the 

notebook  as  D}  meaning  telescope  direct.  Invert  the  telescope,  turn 
on  A,  and  proceed  to  the  other  signals  and  back  again  as  before, 
recording  the  pointings  as  I,  meaning  telescope  inverted. 

These  four  pointings  on  all  the  signals  constitute  a  set,  and 
in  any. set  the  four  pointings  on  any  one  signal  are  evidently  read 
by  the  verniers  at  very  nearly  the  same  point  of  the  limb.  The  use 
of  opposite  verniers  eliminates  errors  of  eccentricity.  Inverting 
the  telescope  eliminates  errors  of  adjustment  in  the  line  of  collima. 
tion  and  standards.  A  multiplication  of  the  pointings  tends  to  reduce 
accidental  errors. 

It  should  be  observed  that  the  transit  is  level  and  accurately  above 
the  station  before  beginning  each  set.  If,  while  observing,  the  levels 
show  a  change,  they  should  not  be  disturbed  until  the  set  is  finished ; 
when,  if  a  change  is  considerable,  the  entire  set  of  readings  should  be 
rejected.  The  stability  of  the  instrument  on  its  tripod  or  other  support 
should  receive  careful  attention. 

The  successive  pointings  should  be  made  as  rapidly  as  consistent 
with  accuracy,  thus  giving  them  a  greater  certainty  of  having  them 
made  all  under  the  same  conditions,  by  reducing  the  time  by  which 
unequal  temperature  affects  on  the  instrument,  or  changes  in  illumina- 
tion of  the  signal,  may  occur. 

When  the  .sun  is  not  obscured,  especially  in  summer,  heated  air  cur- 
rents are  apt  to  render  the  image  of  the  signal  so  unsteady  as  to  make  a 


440  THE  SERVICE  OF  COAST  ARTILLERY 

pointing  to  it  very  uncertain.  To  obtain  an  accurate  bisection  of  a 
distant  signal,  we  must  have  steadiness  of  air  and  good  definition.  It  will 
contribute  to  accuracy  if  the  transit  is  shielded  artificially  from  the 
direct  rays  of  the  sun  when  the  weather  is  not  cloudy. 

In  a  wind  when  the  transit  is  mounted  on  a  tripod,  it  will  often  be 
found  difficult  to  center  it  over  a  station  by  means  of  a  plumb  bob. 
Advantage  may  be  taken  of  the  method  of  inclosing  the  line  and  bob 
in  a  gas  or  sewer  pipe  of  small  bore,  supported  on  the  bottom  on  strips 
or  blocks  of  wood  of  just  sufficient  height  to  permit  seeing  that  the  bob 
is  properly  centered  under  the  pipe. 

After  these  various  sets  of  readings  are  taken  the  accurate  adjust- 
ment of  the  triangle  should  be  made. 

The  Determination  of  the  True  Azimuth. — The  azimuth  of  a  line 
is  the  horizontal  angle  between  the  line  and  a  true  south  line  running 
from  one  of  its  extremities,  the  angle  always  being  measured  from  the 
south  point  as  an  origin  towards  the  right;  that  is,  in  the  same  direction 
as  the  increasing  graduations  on  a  watch.  If  the  direction  of  the  line 
be  between  north  and  east,  its  azimuth  will  be  between  180  and  270 
degrees;  if  between  east  and  south  its  azimuth  will  be  between  270 
and  360.  The  method  of  determining  the  true  azimuth  of  a  base  line 
in  coast  artillery  work  is  that  known  as  the  determination  by  stellar 
observation,  or  observations  on  Polaris. 

For  example,  suppose  in  Fig.  69  that  OT  is  the  base  line  in  question, 
with  the  transit  accurately  centered  over  the  point  0  and  a  signal  or 
target  at  the  other ;  Z,  the  zenith  or  point  directly  overhead  as  pointed 
out  by  a  plumb  line;  HH,  the  horizon.  Planes  passing  through  ZA 
will  cut  the  sphere  in  circles  all  of  which  intersect  the  horizon  at  right 
angles  and  pass  through  the  zenith.  These  are  called  vertical  circles. 
One  of  these ,  ZPN,  will  pass  through  the  point  P  where  the  axis  of  the 
earth  pierces  the  surface  of  the  earth  called  the  pole.  The  projection 
of  the  arc  ZPN  on  the  surface  of  the  earth  gives  the  true  meridian, 
NOS,  and  N  the  north  point  of  the  horizon.  The  arc  PN  or  the 
altitude  of  the  pole  above  the  horizon  is  always  the  latitude  of  0,  the 
observers'  station,  say  37  degrees;  the  remainder  of  the  quadrant  PZ  is 
called  the  co-latitude  and  is  equal  to  53  degrees. 

The  line  of  sight  of  a  transit  in  perfect  adjustment  placed  at  0  and 
pointed  at  N  will,  when  revolved  on  the  trunnions,  pass  successively 
through  P  and  Z.  If  there  were  a  star  permanently  located  at  any 
point  in  this  arc,  as  at  P,  the  determination  of  the  azimuth  OT  or  the 
base  line  would  consist  simply  in  measuring  with  the  transit  the  hori- 
zontal angle  between  two  objects  P  and  T  at  unequal  heights,  in  other 


SEACOAST  ENGINEERING 


441 


words  the  angle  NOT,  which  is  the  azimuth  of  OT  reckoned  from  the 
north.  Increasing  this  by  180  degrees  we  will  have  the  true  azimuth, 
SOT. 

It  happens,  however,  that  there  is  no  star  exactly  at  the  pole  P,  but 
Polaris  indicated  as  St  is  about  one  and  a  fourth  degrees  from  the  pole, 
and  is  the  nearest  star  which,  in  the  absence  of  clouds,  can  be  seen 
readily  with  the  naked  eye  even  in  full  moonlight. 

So  if  S  is  the  star,  the  angle  TOB  between  the  star  and  the  line  is 
measured  with  the  transit.  After  deducting  the  angle  BON  between 


FIG.  69. 

the  star  and  the  meridian  we  have  the  angle  NOT,  which  as  before  is 
the  azimuth  of  the  base  line  from  the  north. 

To  an  observer  facing  the  north  Polaris  appears  to  move  in  a  circle 
around  the  pole  once  in  24  hours  in  the  direction  of  the  arrow  indicated 
on  the  cut,  with  a  radius  of  one  and  a  fourth  degrees  from  the  pole.  (To 
give  some  idea  of  the  extent  of  one  and  one-fourth  degrees  on  the  sphere, 
it  may  be  remembered  that  it  is  one-quarter  the  distance  between  the 
pointers  in  the  Dipper,  or  the  length  occupied  by  two  full  moons  and  a 
half  placed  side  by  side.) 

The  same  is  true  of  all  other  stars,  each  within  its  own  radius;  and 


442 


THE  SERVICE  OF  COAST  ARTILLERY 


this  affords  a  means  of  both  finding  Polaris  at  any  hour  and  locating  the 
pole  approximately.  The  line  joining  the  pointers  passes  very  near 
to  Polaris  and  the  line  joining  Polaris  and  the  star  at  the  bend  of  the 
handle  of  the  Dipper  passes  over  the  pole  one  and  a  fourth  degrees  from 
Polaris. 

TO    DETERMINE    THE    TRUE    AZIMUTH 

The  mean  sun,  by  whose  motion  ordinary  timepieces  are  regulated, 
moves  daily  around  the  pole  in  a  circle,  with  a  longer  radius  but  in  the 
same  direction  as  Polaris.  Polaris,  however,  moves  a  little  faster  in 
an  angular  sense  than  the  sun,  completing  the  circuit  3.94  minutes 
sooner.  Once  a  year,  therefore,  the  star  Polaris  will  overtake  the  sun, 
and  the  date  upon  which  this  occurs  is  given  in  the  table  following: 


TABLE  A 
CIVIL  DATES  (OR  EPOCHS)  WHEN  POLARIS  PASSES  THE  MEAN  SUN 


Year. 

Epoch. 
April. 

Year. 

Epoch. 
April. 

Year. 

Epoch. 
April. 

Year. 

Epoch. 
April. 

1901 

13  0 

1909 

13   8 

1917 

14   6 

1925 

15  3 

1902 

13  4 

1910 

14   2 

1918 

15  0 

1926 

15  6 

1903 

13  7 

1911 

14  5 

1919 

15  3 

1927 

15  9 

1904 

13  1 

1912 

13  9 

1920 

14  7 

1928 

15  3 

1905 

13  4 

1913 

14  2 

1921 

15  0 

1929 

15  6 

1906 

13  8 

1914 

14  6 

1922 

15  3 

1930 

15  9 

1907 

14  1 

1915 

14  9 

1923 

15  6 

1931 

16  2 

1908 

13  5 

1916 

14  3 

1924 

15  0 

1932 

15  6 

By  the  use  of  this  table  the  position  of  Polaris  in  its  daily  path  at 
any  instant  during  the  ensuing  year  can  be  determined.  In  other  words, 
it  would  be  ahead  of  the  sun  by  3.94  minutes  times  the  number  of  days 
and  fraction  of  a  da,v  in  the  interval.  The  position  of  the  sun  itself  is 
known  by  the  use  of  the  corrected  watch  time.  For  example,  suppose 
Polaris  to  pass  the  mean  sun  on  April  14.1.  The  civil  day  beginning 
at  midnight,  this  date  is  really  2:24  A.M.,  April  14th.  What  is  its  posi- 
tion in  its  circular  path  on  June  24th  at  4:30  P.M.?  The  interval  to 
the  nearest  tenth  is  71.6  days,  and  71.6  multiplied  by  3.94  equals  4 
hours  and  42  minutes,  which  is  the  time  Polaris  is  ahead  of  the  sun. 
The  sun  is,  as  stated,  4^  hours  from  the  meridian.  Therefore,  Polaris 
is  9  hours  and  12  minutes  from  the  meridian,  or,  in  circular  measure, 
138  degrees  from  the  same.  It  is  in  the  first  half  of  its  daily  path,  or  at 


SEACOAST  ENGINEERING 


443 


some  such  point  as  S  prime,  in  Fig.  69,  and  the  hour  angle  is  indicated 
by  the  angle  in  the  figure  ZPS  prime,  which  is  equal  to  138  degrees.  In 
the  spherical  triangle  ZPS  prime  we  have  known  the  side  ZP,  which 
is  equal  to  the  CO — latitude  of  the  station,  or  53  degrees;  the  side  S 
prime,  equal  to  the  constant,  equal  to  1  degree  and  13  minutes,  and  the 
angle  at  P,  equal  to  138  degrees.  The  angle  at  Z  may  therefore  be 
computed,  and  it  is  the  angular  distance  of  Polaris  west  of  the  meridian  at 
4 :30  P.M.,  June  24th,  which  is  the  same  as  the  angle  BON  on  the  surface 
of  the  earth.  By  varying  the  hour  angle  at  P  from  zero  to  360  degrees, 
a  table  of  azimuths  of  Polaris  at  any  latitude  can  be  constructed  for 
each  hour  of  the  24.  The  table  for  latitude  40  degrees  north  is  given 
below: 

TABLE  B 

ANGULAR  DISTANCE  OF  POLARIS  FROM  THE  MERIDIAN  FOR 
DIFFERENT  HOUR-ANGLES  (#)  IN  APRIL,  1900,  LATITUDE  40° 
(CALLED  THE  AZIMUTH  OF  POLARIS) 


H,  hours  .    .        

0 

1 

234 

5 

6 

7 

8 

9 

10 

11 

12 

Az.  minutes  of  arc  .  . 

0 

25 

49     69     84 

93 

96 

92 

82 

67 

47 

24 

0 

H,  hours  . 

24 

?3 

22     21     20 

19 

18 

17 

16 

15 

14 

13 

12 

TABLE  C 
FACTOR   FOR   YEAR  AND   LATITUDE 


Lat. 

1900 

1910 

1920 

1930 

20° 

0  82 

0  78 

0  75 

0  72 

30° 

0  88 

0  85 

0  81 

0  77 

40° 

1  00 

0  96 

0  92 

0  87 

50° 

1   10 

1   14 

1  09 

1  04 

The  problem  of  determining  the  true  azimuth  of  a  base  line  consists 
in  measuring  at  any  convenient  time  the  horizontal  angle  between 
Polaris  and  the  line  to  be  established  and  then  applying  thereto  the 
angular  distance  of  Polaris  from  the  meridian;  that  is,  the  angular 
distance  at  the  moment  of  observation.  The  solution  of  the  following 
problem  illustrates  the  method  followed: 


444  THE  SERVICE   OF  COAST  ARTILLERY 

Find  the  azimuth  of  the  base  line  NO,  Fig.  69,  the  latitude  of  station 
being  37  degrees,  longitude  70  degrees  west.  The  angle  between 
Polaris  and  the  artificial  star  was  200  degrees.  The  time  of  sighting 
on  star  by  the  watch  was  10  P.M.,  July  26,  1904.  The  watch  was  30 
seconds  fast. 

Solution. — The  transit  is  adjusted  beforehand  and  by  daylight,  and 
set  up  at  the  point  0.  A  post  is  sunk  firmly  in  the  earth  at  the  point 
T1,  and  on  a  separate  surface  are  nailed  two  strips  pointing  in  the 
direction  of  the  distant  station  where  the  observation  is  to  be  made, 
or  at  the  point  0.  Between  these  two  stripes  a  small  box  opened  at  the 
rear  is  placed  and  a  bullseye  lantern  is  put  in  with  its  lens  against  the 
front  wall  of  the  box.  In  the  top  over  the  lantern  a  hole  is  cut  for  the ' 
escape  of  the  smoke,  and  in  the  front  face  at  the  height  of  the  lens  a 
small  circular  hole  is  cut  through, the  box  so  that  the  light  is  visible 
from  the  point  of  observation.  This  hole  should  be  made  very  small 
so  that  the  light  will  have  the  appearance  of  a  star  when  sighted  upon 
with  the  transit.  First  with  the  telescope  direct  read  on  star  and  then 
on  the  signal  or  artificial  star.  Invert  the  telescope  and  read  on  signal 
and  then  on  the  star.  For  greater  accuracy  a  second  set  of  readings 
may  be  taken.  As  assumed  in  the  problem,  the  angle  between  Polaris 
and  the  artificial  star  was  found  to  be  200  degrees.  The  solution  of  the 
rest  of  the  problem  is  therefore  as  follows : 

Corrected  watch  time=9h59m30s  standard  time. 
Local  time  =9h  59m  30s  +20m. 
15)5°  =20  minutes. 

Therefore  corrected  time  of  observation  =  10h  19m  30s,  July  26,  1004. 
Interval  between  epochs  = 


May  

.  ..     31. 

June 

30 

Julv  . 

.  .  .     25.93 

104.83  days 

3. 94mX  104.83  =412.99m  =6h  52m  59.4s  =time  Polaris  is  in  advance 
of  the  sun. 

The  sun  is  10h  19m  30s  from  the  meridian. 

Therefore  Polaris  is  17h  12m  29s  from  the  meridian  =  hour  angle. 


SEACOAST  ENGINEERING  445 

From  Table  B 
Azimuth  Polaris  =92.83'+. 
Correcting  (from  Table  C)  for  year  and  latitude. 

1900  1904  1910 

37°  .964  .949  .927 

92.83'  X. 949  =  88.096'  =  1°  28. 1'  5" 

Azimuth  from  N=201°  28'  5". 
"   S=  21°  28' 5". 


LOCATION    OF    PINTLE    CENTERS 

The  center  of  the  true  or  pintle  surface  of  the  ring  is  the  point 
required.  This  point  may  be  obtained  after  the  base  ring  has  been  set 
and  before  the  racer  has  been  put  in  position,  or  even  after  the  gun  and 
carriage  have  been  mounted.  For  example,  suppose  the  racer  net- 
to  be  in  position,  and  that  the  carriage  has  not  been  mounted.  A 
tripod  made  of  pieces  of  scantling  is  placed  at  the  center  of  the  pit  with 
legs  properly  braced  to  prevent  motion,  or  built  up  by  a  box  from  the 
center  of  the  pit  at  the  bottom  until  the  upper  surface  is  nearly  at  the 
level  where  it  is  intended  to  locate  the  center  of  the  base  ring.  Nail  on 
the  top  of  this  pile  a  piece  of  dressed  pine  4x4  feet  square  for  use  in 
making  marks  with  a  pencil  or  sharp  pointed  instrument.  The  diameter 
of  the  base  ring  may  be  found  from  the  official  drawings,  or  it  may  be 
measured  very  closely  with  a  steel  tape.  With  the  marking  point  of 
a  trammel  set  as  nearly  as  possible  to  the  radius,  and  with  the  caliper 
point  bearing  at  the  particular  height  against  the  pintle  surface,  strike 
an  arc  across  the  cap.  Do  the  same  at  three  other  points  around  the 
ring  90  degrees  apart,  taking  care  that  the  caliper  point  is  always  at 
the  same  height.  If  these  four  arcs  all  pass  through  a  given  point  this 
is  the  center  sought.  If  not,  the  distance  between  the  points  of  the 
trammel  should  be  altered  until  two  opposite  arcs  slightly  overlap 
and  the  two  points  of  intersection  come  on  the  cap.  Over  this  point 
a  suitable  signal  with  pointed  end  may  be  erected,  held  in  a  vertical 
position  by  wire  guys  fitted  with  turnbuckles,  and  of  sufficient  length 
to  be  seen  from  two  or  more  triangulation  stations.  This  will  usually 
require  the  signal  to  project  above  the  parapet,  necessitating  a  length 
of  from  15  to  20  feet,  according  to  the  caliber  of  the  gun.  Sections  of 
gas-pipe  fitted  together  make  a  good  signal,  and  one  having  but  little 
flexure.  By  this  signal  the  pintle  center  is  located  by  triangulation. 


446 


THE   SERVICE   OF   COAST  ARTILLERY 


If  a  trammel  is  not  at  hand  and  one  cannot  be  improvised,  the  following 
devices,  or  others  which  may  suggest  themselves,  may  be  employed. 

In  Fig.  70,  AB  is  a  straightedge  of  scantling  (supported,  if  necessary, 
at  intermediate  points  to  avoid  sag)  laid  as  nearly  as  practicable  over 
the  center,  and  ab  marked  or  scratched  on  the  cap.  AB  is  bisected  by 
a  steel  tape,  and  the  point  e  located,  at  which  a  perpendicular  to  ab  is 
erected  in  the  ordinary  manner.  The  straightedge  is  then  transferred 
to  a  position  CD,  estimated  as  perpendicular  to  the  former,  and  the  point 
/  determined  as  was  e.  The  intersection  of  the  perpendiculars  at  e  and 
/  is  the  center. 


FIG.  70. 


FIG.  71. 


It  may  be  well  to  mark  the  points  A  and  B  permanently  on  the 
straightedge  by  means  of  solid  stops  which  will  bear  against  the 
pintle  surface;  these  stops  being  a  little  nearer  together  than  the 
pintle  diameter.  The  point  e  may  then  be  marked  on  the  edge  once 
for  all. 

Where  the  base  ring  is  made  in  two  parts,  the  line  connecting  the 
joints  is  evidently  a  diameter  of  the  ring,  and  the  straightedge  care- 
fully adjusted  along  this  diameter,  and  accurately  bisected,  gives  the 
center. 

In  Fig.  71,  A  Bed  represents  a  scantling  T  square  with  the  pieces 
halved  into  each  other,  supported  as  may  be  necessary,  and  the  inner 
edge  cd  bisecting  AB  at  right  angles,  as  shown  by  a  "square."  The 
line  cd  is  marked  on  the  cap,  and  the  T  square  transferred  to  a  position 
estimated  as  perpendicular  to  the  former.  The  intersection  of  the 
two  lines  cd  gives  the  center. 


SEACOAST  ENGINEERING  447 

In  emplacements  for  an  A.  R.  F.  disappearing  carriage,  it  will  be 
most  convenient  to  use  the  inner  base  ring.  The  central  blocking  will 
be  very  low.  In  emplacements  for  non-disappearing  carriages  (com- 
monly called  barbette)  the  diameter  of  the  pintle  surface  is  so  small, 
and  the  center  so  readily  found  and  tested,  that  no  remark  is  necessary. 

It  will  be  remembered  that  for  the  best  results  each  angle  of  a 
triangle  should  be  directly  measured  in  order  that  a  suitable  adjustment 
may  be  made.  In  emplacements  for  disappearing  guns,  however, 
whether  L.  F.  or  A.  R.  F.,  the  pintle  center  cannot  be  conveniently 
occupied  by  a  transit  (even  though  the  point  be  carried  upward  by  a 
plumb  line),  on  account  of  the  diameter  of  the  emplacement,  and  the 
height  of  the  parapet,  over  which,  in  the  general  case,  it  would  be 
necessary  to  obtain  a  clear  view. 

In  barbette  emplacements  the  transit  may  be  very  conveniently  set 
over  the  pintle-center  so  as  to  give  a  free  view  over  the  parapet.  This 
point  is  therefore  a  very  advantageous  observation  station,  and  should 
be  always  occupied,  both  as  an  aid  to  its  own  accurate  location  in  the 
triangulation  scheme,  and  also  in  the  location  of  reference  points  in  the 
field  of  fire  for  purposes  of  orientation. 

With  mortar  emplacements,  where  the  racers  have  not  been  put  in 
position,  the  same  methods  are  applicable  as  in  the  case  of  emplacements 
for  disappearing  guns.  It  will,  however,  usually  be  found  necessary  to 
locate  trigonometrically,  not  the  individual  mortar  centers,  but  a  single 
directing  point  for  the  battery  (which  may  well  be  on  the  parapet) ,  or 
at  most  the  centers  of  the  individual  pits.  In  the  latter  case  the  center 
of  the  rectangle  of  the  four  base  rings  may  be  easily  marked  on  the  floor 
of  each  pit  with  quite  sufficient  accuracy,  and  signals  erected  at  these 
points  as  before  described.  It  will  not  be  convenient  to  occupy  such 
pit  stations  with  a  transit;  but  the  directing  point  of  the  battery 
should  always  be  occupied. 

In  all  these  cases  the  verticality  of  the  signal  throughout  its  whole 
extent  should  be  secured  and  tested  by  a  transit,  immediately  before  any 
triangulation  work. 

To  Find  the  Center  of  Motion. — When  the  carriage  and  gun  have  been 
mounted  over  a  base  ring  properly  leveled,  the  center  of  motion  of  the 
gun,  when  turned  in  azimuth,  will  practically  coincide  with  the  center  of 
the  pintle  surface,  and  may  be  found  with  either  barbette  or  disappear- 
ing mounts  as  follows :  With  the  gun  in  the  firing  position  and  at  about 
the  limit  of  its  play  in  azimuth,  locate  two  points  of  the  "line  of  metal" 
(or  highest  element)  on  each  portion  of  the  contour  of  the  gun.  Snap 
a  chalk  line  between  these  points.  This  chalk  mark  on  the  gun  lies 


448  THE   SERVICE   OF  COAST  ARTILLERY 

directly  over  the  center  of  the  pintle  surface.  Set  up  a  transit  on  the 
parapet  at  a  distance  of  50  yards  or  thereabouts,  and  depress  the  gun 
until  the  chalk  mark  is  visible  throughout  its  whole  extent.  (It  may 
be  found  desirable  to  raise  the  transit  on  blocks  one  or  two  feet.) 
Traverse  both  gun  and  transit  until  by  trial  the  intersection  of  the  cross 
wires  will  run  accurately  along  the  whole  mark  as  the  telescope  is  elevated 
and  depressed.  The  transit  is  now  pointing  along  a  diameter  of  the 
pintle  surface,  and  must  not  be  disturbed  in  azimuth.  Traverse  the  gun 
approximately  90°,  bring  it  to  0°  elevation,  and  then  move  along  the 
chalk  mark  a  pencil,  wire,  or  flat-headed  nail  inverted,  until  its  base 
is  accurately  on  the  line  of  sight  of  the  transit.  The  point  thus  deter- 
mined is  evidently  on  two  diameters  of  the  pintle  surface — one  indicated 
by  the  chalk  mark,  and  one  by  the  line  of  sight  of  the  transit.  It  is  there- 
fore at  the  center — which  supposition  should  be  tested  by  traversing 
the  gun  through  a  considerable  arc  to  the  right  and  left.  Scratch  the 
chalk  mark  at  the  exact  point  by  the  pencil  or  nail.  Over  this  point  a 
small  target  may  be  set  up  and  securely  fastened  to  the  gun,  as  a 
signal  for  triangulation  purposes,  and  the  pintle  center  located  trigo- 
nometrically  thereby.  The  pattern  shown  in  Fig.  72  has  been  found 
to  answer  perfectly.  AB  is  a  half-inch  board  about  3  by  8  or  10  inches, 
fastened  by  brads  to  two  cross  shoes,  whose  lower  surfaces  are  hollowed 
out  to  fit  the  curvature  of  the  gun  hoops.  Through  a  hole  in  the 
middle  of  the  board  passes  a  small  post  P,  of  the  proper  diameter  for 
a  signal,  extending  10  or  12  inches  above,  suitably  braced,  and  a  fraction 
of  an  inch  below.  Into  the  middle  of  its  lower  end  is  driven  an  iron  or 
steel  point  so  that  when  the  shoes  are  placed  on  the  gun,  this  point  will 
just  touch  the  gun  or  very  nearly  so.  Openings  are  cut  in  the  board  and 
it  is  cut  away  at  the  sides  to  allow  of  properly  placing  the  pin  over  the 
point  on  the  chalk  mark.  The  whole  may  be  securely  bound  in  place 
by  twine  or  straps  attached  to  the  parts  of  the  carriage,  and  will  be 
immovable  in  any  ordinary  wind. 

The  above  method  of  finding  the  center  of  motion  applies  strictly 
only  to  barbette  and  the  later  models  of  disappearing  mounts,  where  the 
point  in  question  falls  either  on  the  body  of  the  piece  or  the  trunnion 
hoop — surfaces  which  are  level  when  the  gun  is  at  zero  degrees  elevation. 
In  the  disappearing  model  of  1894,  however,  the  point  falls  on  the 
sloping  surface  of  one  of  the  chase  hoops.  In  observing  this  point 
during  the  triangulation,  the  post  P  must  be  vertical.  Therefore,  when 
the  piece  is  traversed  90  degrees  in  order  to  locate  the  pencil  or  nail  as 
before  described;  the  gun  should  not  be  set  at  zero,  but  at  such  elevation 
that  the  post  will  be  vertical  when  in  position.  This  may  be  accom- 


SEACOAST  ENGINEERING 


449 


plished  by  placing  the  target  of  Fig.  72  on  the  hoop  in  question  and 
testing  the  verticality  of  the  post  by  the  vertical  motion  of  the  transit, 
altering  the  elevation  of  the  gun  until  the  desired  result  is  obtained. 
The  elevation  of  the  gun  should  not  be  changed  during  the  subsequent 
triangulation. 

On  account  of  irregularities  in  the  contour  of  a  gun,  it  will  be  found 
best,  in  marking  the  line  of  metal,  to  snap  the  chalk  line  on  each  portion 
of  the  surface  separately,  i.e.,  on  the  body,  on  the  trunnion  band,  etc. 

The  line  of  metal  may  be  found  as  follows:  Clear  the  vent,  close  the 
breech  and  place  in  the  muzzle  an  open  bore  sight  having  white  cross 


FIG.  72. 

threads,  i.e.,  fine  white  cord  or  fine  wire  wrapped  with  white  insulating 
material. 

Set  up  a  transit  on  the  parapet  as  before,  point  into  the  muzzle  and 
by  elevating  and  traversing  both  gun  and  transit,  bring  the  cross  wires 
of  the  transit,  the  cross  threads  in  the  muzzle,  and  the  axis  of  the  vent 
in  line.  Depress  the  gun,  and  with  the  vertical  wire  of  the  transit,  locate 
by  a  pencil  or  other  sharp  point  several  points  of  the  line  of  metal  and 
snap  a  chalk  line  as  before. 

With  mortars,  the  problem  of  location  of  the  directing  point  of  the 
battery  or  of  the  centers  of  the  different  pits,  is  evidently  the  same  as 
before  the  mortars  were  mounted. 

Orientation  of  Gun  and  Mortar  Azimuth  Circles. — These  circles, 
when  received  from  the  arsenals,  have  the  degree  marks  cut  on  them, 
but  the  proper  numbering  of  the  marks  is  necessarily  postponed  until 


450 


THE  SERVICE  OF  COAST  ARTILLERY 


the  circles  are  in  position.  A  brass  subscale,  whose  least  reading  is 
five  one-hundredths,  is  screwed  to  the  racer — the  screw  holes  being 
slotted  to  permit  of  lateral  movement  and  adjustment  of  the  scale. 
The  complete  orientation  of  a  circle  consists  in  the  proper  .numbering 
of  the  degree  marks,  and  the  proper  setting  of  the  subscale,  so  that 
when  the  gun  points  to  the  true  South  the  reading  shall  be  0°,  or  when 
pointing  to  any  object  whose  azimuth  is  known,  the  reading  shall  be 
that  azimuth. 

1.  Guns. — In  order  to  do  this,  and  as  a  check  from  time  to  time 
in  the  future,  the  azimuth  from  the  pintle-center  of  one  or  more  points 
in  the  field  of  fire  should  be  accurately  determined.  These  points  may  be 
either  natural  or  artificial,  but  must  be  clearly  visible  through  the 
bore  of  the  gun.  For  example,  the  tip  of  a  lighthouse  or  other  tower, 
a  spire,  the  vertical  edge  of  a  structure,  a  certain  pile  of  a  distant  wharf, 


FIG.  73. 


or  a  pile  or  other  target  specially  erected,  a  paint-mark  on  a  vertical 
rock  cliff,  or  a  flagstaff,  would  all  answer.  The  azimuth  of  such  points 
from  the  guns  should  be  found  at  the  same  time  that  the  gun  pintles  are 
located.  For  example,  in  case  the  pintle  centers  have  been  occupied 
by  a  transit  as  on  barbette  mounts,  the  azimuth  from  the  gun  of  any 
object  in  the  field  of  fire  may  be  directly  determined  at  the  same  time 
by  measuring  the  angle  between  one  of  the  base  ends  (or  other  established 
point)  and  the  object  in  question.  As  this,  however,  does  not  of  itself 
give  the  range  to  such  points,  it  is  usual  to  determine  both  their  range 
and  azimuth  by  triangulation.  Thus  in  Fig.  73,  if  EF  is  a  line  whose 
azimuth  and  length  are  known,  G  the  gun  center,  and  L  the  reference 
point  in  question,  then  the  distance  and  azimuth  of  L  from  G  may  be 
found  by  sighting  from  E  and  F  on  each  of  the  other  three  points. 
If  G  and  L  can  also  be  used  as  observing  stations,  it  will  add  to  the 
accuracy  of  the  determination.  A  complete  solution  of  the  following 
problem  illustrates  the  method: 


SEACOAST  ENGINEERING 


451 


PROBLEM. — To  determine  the  azimuth  and  range  of  "lighthouse" 
from  Gun  No.  2,  Battery  -  — .  Same  to  be  used  as  datum  point 

for  orientation  of  gun. 

Method. — The  pintle  center  was  located  as  previously  described. 

The  following  observations  were  then  made: 


Station  at 

On. 

Reading. 

Angle. 

Remarks. 

E 

F 
G 

L 

3°  50' 
60°  54' 

117°  06' 

57°  04' 
56°  12' 

One  end  of  base  line. 
Gun  No.  2,  Battery  . 

Point  on  Lighthouse. 

113°   16' 

F 

G 
L 
E 

23°  15'  1 
41°  51'  / 
105°  48' 

18°  36' 
63°  57' 

82°  33' 

See  diagram,  'Fig.  73. 

The  following  table  shows  the  solution: 


TABLE   OF    DATA 


From 

To 

Azimuth. 

Range,  Yards. 

E 

F 

145°  47'  23" 

349  •  184 

F 

E 

325°  47'  23" 

349  .  184 

E 

L 

259°  03'   23" 

6460.496 

L 

E 

79°  03'  23" 

0460  496 

L 

F 

81°  50'   23" 

6605.909 

F 

L 

261°  50'   23" 

6605.909 

L 

G 

*83°    10'   35.1" 

6179.29 

G 

L 

t263°   10'   35.1" 

6179.29 

G 

E 

22°   51'  23" 

534.341 

E 

.     G 

202°   51'  23" 

534.341 

G 

F 

63°   14'   23" 

452.354 

F 

G 

243°   14'   2:;" 

452.354 

By  proof  method  83'  10'  39.8". 


t  By  proof  method  233°  10'  39.8' 


Solution  for  Azimuth  and  Range  (only) . 

Z  FGE  =  180°  -  (18°  36'  +  63°  57')  =  40°  23'. 
sin  82°  33' :  sin  40°  23' :  :  EG :  EF. 
EF  sin  82°  33' 


/.  EG 


sin  40°  23' 


452  THE  SERVICE  OF  COAST  ARTILLERY 

logEF=   3.0201844 
(in  ft.) 
log  sin  82°  33'=   9.99632 

13.0165044 
log  sin  40°  23'=   9.811505 

log  EG  =  3.2049994 
/.  EG=  1603.024  ft.  =  534.341  yards. 
Z#LF=180°-(63°  57' +  57°  04' +  56°  12')  =2°  47'. 
sin63°57':sin2°47'::#L:E'F. 
j,7      EF  sin  63°  57' 

sin  2°  47' 

logEF=  3.0201844 
log  sin  63°  57'=   9.953475 

12.9736594 

log  sin    2°  47'  =   8.68627 

log  EL  =   4.2873894 
/.  EL=  19381. 49  ft.  =  6460.496  yards. 
<2  +  L=180°-56°  12' =  123°  48'. 

19381.491  - 1603.024  rpo      , 

tan  i(G- L)  =  19381  491  + 1603.024  ° 

19381.491  19381.491 

1603.024  1603.024 

(1)     17778.467  (2)     20984.515 

log  (1)=  4.24990073 
log  cot  28°  06'=    .27250 

4.52240073 

log  (2)  =4.3218972 


log  tan  J(G-  L)  =    .20050353 
.-.    tan  KG-  £)=  57°  46'  47.9". 
*(G  +  L)=61°  54' 
i(G-L)=57°46'47.9" 

G=119°40'  47.9" 
L=     4°  07'  12.1" 
Az.  EF  (given)  =  145°  47'  23" 
113°  16' 


Az.  #L  =  259°  03'  23" 


SEACOAST  ENGINEERING  453 


}// 


Az.  LE=   79°  03'  23' 
'=     4°  07'  12.1' 


i  // 


Az.  LG=   83°  10'  35.1' 

Az.  GL  =  263°  10'  35.1"  =  (gun  azimuth) 

Sin  119°  40'  47.9":  :sin  56°  12': :  19381.491  :GL. 

19381.491  sin  56°  12' 
'"'    '  sin  119°  40'  47.9" 

log  19381.491-    4.2873894 
log  sin  56°  12'=   9.919595 

14.2069844 
log  sin  119°  40'  47.9"=   9.938924 

logGL  =   4.2680604 
/.  GL=  18537.87  ft,  =  6179.29  yards  =  range. 

Solution  for  finding  other  sides   of  quadrilateral    and    as    a   check   on 
foregoing  solution. 

Sin  57°  04': sin  40°  23'::FG:EF. 
EFsmo7°04' 

sin  40°  23' 
\ogEF=  3.0201844 
log  sin  57°  04'  =   9.92392 

12.9441044 

loo-  sin  40°  23'=   9.811505 
logFG=   3.1325994 

/.  FG=  1357.0606  ft.  =  452.354  yards, 
sin  G:sinF::FL:GL. 

GL  sin  G 
•'•  FL=-sin^ 
log  sin  19°  56.2'=   9.53273 
log(7L=   4.26806 

13.80079 
log  sin  18°  36'=   9.50374 

logFL=   4.29705 
.-.  FL=  19817.727  ft.  =  6605.909  yards. 


454  THE  SERVICE   OF  COAST  ARTILLERY 

Proof  of  Solution  for  L  's  G  and  L. 

_a  _  19817.729 

"6  "1357.0606 
tan  i(G-L)=tan  (x-4 
log  a  =  4.29705 
log  6  =  3.  132599 

log  tan  z  =  1.164451 

.;.  x  =  86°  04.95' 
(x-  45°)  =41°  04.95' 
log  tan  41°  04.95'  =  9.940427 

log  tan  i(£  +  £)  =    -78580 


log  tan  i  (#-£)  =   .726227 
i(£-L)=   79°  21.72' 
-   80°  42' 


/.  G=  160°  03.72'  =  160°  03'  43.2" 
L  =      1°  20.28'=      1°  20'  16.8" 

Having  located  at  least  two  such  reference  points,  place  bore  sights 
in  the  breech  and  muzzle  of  the  gun,  the  sights  having  black  cross 
threads,  and  turn  the  gun  on  one  of  the  points  as  L,  whose  azimuth  from 
G  is,  for  example,  263.17°.  Loosen  the  clamp  SCI-EWS  of  trn  subscale 
and  slip  the  scale  to  the  right  or  left  until  its  .17  division  lies  directly 
over  some  graduation  line  of  the  circle — the  zero  of  the  scale  thus  being 
.17  to  the  left  of  this  line..  By  alternate  movements  of  the  screws,  set 
them  moderately  well  home,  taking  care  that  the  subscale  does  not 
move.  By  means  of  a  steel  punch  stamp  this  line  263.  As  the  gun 
now  lies  the  circle  reading  is  263.17  degrees,  as  it  evidently  should 
when  directed  on  a  point  whose  azimuth  is  263.17  degrees.  Proceed 
around  the  circle  to  the  left,  stamping  the  lines  successively  262,  261, 
etc.  Turn  the  gun  on  another  reference  point  for  verification.  If  a 
discrepancy  be  found  to  exist  the  computation  of  the  azimuths  of  the 
points  should  be  re-examined.  If  no  error  be  found,  the  triangulation 
should  be  repeated.  When  substantial  verification  has  been  obtained, 
the  screws  should  be  set  fully  home,  but  without  inserting  dowels,  as 
these  prevent  subsequent  adjustment  of  the  scale. 

Whether  the  telescopic  sight  may  be  substituted  in  this  operation 
for  the  bore  sights  is  a  matter  of  calculation  and  judgment.  For 
example,  suppose  a  sight  accurately  adjusted  to  parallelism  with  the 
axis  of  the  bore  and  distant  therefrom  4  feet  when  on  the  sight  standard. 


SEACOAST  ENGINEERING  455 

If  this  sight  be  directed  on  a  reference  point  1,000  yards  distant,  the 
gun  will  point  4^  minutes  to  the  right  or  left,  and  hence  the  subscale, 
if  set  accordingly,  will  always  be  4^  minutes  in  error.  When  firing 
by  Case  III  this  will  cause  a  deviation  error  of  about  13  yards  at  a  range 
of  10,000  yards.  If  the  sight  be  nearer  the  axis,  or  if  it  be  adjusted 
to  intersect  the  axis  of  the  bore  at  6,000  yards;  or  if  the  reference  point 
be  more  distant  or  the  range  less  than  10,000  yards,  the  error  will  be 
less. 

Mortars. — Since  a  view  of  the  field  of  fire  from  mortar-pits  is 
impossible  unless  high  trestles  or  blocking  be  erected,  the  use  of  distant 
reference  points  in  orienting  the  circles  will  in  general  be  impossible. 
There  should ;  whenever  practicable,  be  at  least  one  permanent  point 
established  on  the  parapet  (this  may  be  a  cross  cut  in  the  concrete), 
whose  azimuth  from  some  visible  point  is  known.  From  this  point 
a  line  of  known  azimuths  may  be  run  to  a  point  near  the  crest  of  the 
parapet,  over  which  a  transit  may  be  set  up,  and  by  elevating  the 
mortars  a  view  through  the  bore  of  each  obtained.  The  remainder  of 
the  operation  is  the  same  as  in  case  of  guns.  It  may  be  found  that  a 
single  position  of  the  transit  will  answer  for  more  than  one  pit. 

Leveling. — The  principal  leveling  problems  which  need  be  considered 
in  connection  with  seacoast  works  are  the  determination  of  the  height 
of  gun  trunnions,  and  the  trunnions  of  D.  P.  F.  instruments,  above  mean 
low  water. 

At  each  post  will  be  found  one  or  more  permanent  marks,  called 
"  bench  marks/'  whose  location  and  height  above  mean  low  water 
have  been  determined  and  recorded.  These  data  may  be  obtained 
either  from  the  artillery  engineer  of  the  post,  or  from  the  office  of  the 
district  engineer.  The  height  of  any  given  point  above  such  bench 
mark  is  then  obtained  by  leveling,  and  to  this  height  is  added  the 
height  of  the  bench.  The  result  is  the  height  of  the  given  point  above 
mean  low  water. 

The  instruments  required  are  the  engineer's  Y  level  and  the  leveling 
rod.  The  adjustments  of  the  former  should  be  carefully  made,  and 
to  provide  a  stable  rest  for  the  latter  during  the  work,  an  iron  pin  may 
be  carried  along  and  driven  in  the  ground  as  required. 

The  difference  of  level  between  a  bench  and  any  other  desired  point 
may  be  found  as  follows:  Set  up  the  Y  level  in  any  convenient  position, 
from  which  the  leveling  rod,  when  held  on  the  bench,  will  be  clearly 
visible.  The  rod  should  be  balanced  by  hand  in  a  vertical  position. 
Read  the  rod.  This  reading  is  called  a  back  sight,  and  is  evident!}' 
the  height  of  the  axis  of  the  telescope  above  the  bench.  Pace  the 


456  THE   SERVICE   OF  COAST  ARTILLERY  ' 

distance  from  bench  to  instrument  when  possible;  if  not,  carefulty 
estimate  the  same.  Send  the  rod  forward  in  the  general  direction 
required,  a  distance  equal  to  the  last,  determined  by  pacing  or  estima- 
tion. Drive  the  pin  in  the  ground,  and  rest  the  rod  vertically  on  the 
same.  Turn  the  instrument  and  read  the  rod,  noting  that  the  bubble 
is  level.  This  reading  is  called  a  foresight,  and  is  evidently  the  height 
of  the  axis  of  the  telescope  above  the  pin. 

The  back  sight,  diminished  by  the  fore  sight,  is  therefore  the  differ- 
ence of  level  between  the  bench  and  pin.  If  the  difference  be  positive, 
the  pin  is  higher  than  the  bench;  if  negative,  it  is  lower.  It  will  be  noted 
in  the  foregoing  that  the  instrument  has  not  been  changed  in  position 
between  the  back  and  foresights.  It  has  simply  been  turned  in  azimuth, 
and  its  level  corrected  when  necessary. 

Now  carry  the  instrument  forward  in  the  general  direction  required, 
set  up  and  read  on  the  rod  in  its  last  position.  This  is  another  back- 
sight; and  in  general  any  reading  on  the  rod  held  over  a  point  whose 
height  is  known,  or  which  may  be  calculated  from  previous  readings, 
is  called  a  back  sight,  while  a  reading  on  a  point  whose  height  is  as  yet 
unknown,  is  called  a  fore  sight. 

Continue  in  this  manner,  taking  a  back  and  fore  sight  at  each  posi- 
tion of  the  instrument,  the  last  fore  sight  being  taken  on  the  rod  when 
resting  on  the  point  whose  height  is  required.  Then,  the  sum  of  the 
back  sights,  diminished  by  the  sum  of  the  fore  sights,  gives  the  elevation 
of  the  final  point  above  the  bench. 

For  manifest  reasons  a  cloudy  day  is  best  suited  for  this  work,  and 
to  secure  stability  of  both  instrument  and  rod,  one  should  be  selected 
when  there  is  but  little  wind. 

For  any  one  position  of  the  instrument,  the  two  sights — back  and 
fore — should  be  of  about  equal  length.  This  eliminates  errors  due  to 
imperfect  adjustment  of  the  instrument.  For  example,  if,  when  the 
bubble  is  in  the  middle  of  its  tube,  the  line  of  sight  is  inclined 
upwards  by  a  small  angle,  then  it  has  this  same  inclination  to  the 
horizontal  on  both  back  and  fore  sights;  and  if  the  lengths  of  the  sights 
are  equal,  the  two  rod  readings  will  be  equally  in  excess  of  their  propel 
values,  the  error  disappearing  when  their  difference  is  taken.  This  pre- 
caution will  also  eliminate  in  a  considerable  degree  the  effects  of  unequal 
refraction  which  occur,  especially  in  summer,  if  the  sights  vary  greatly 
in  length.  It  also  eliminates  the  effect  of  the  earth's  curvature,  which, 
at  a  distance  of  one-half  mile  from  the  bench,  amounts  to  2  inches, 
at  one  mile  to  8  inches,  at  two  miles  to  2  feet  8  inches,  etc.,  increasing 
as  the  square  of  the  distance. 


SEACOAST  ENGINEERING  457 

i 
When  it  is    impossible    to  make  the  back  and  foresights  of  equal 

length,  the  inequality  should  be  balanced  off  at  the  next  or  some 
subsequent  setting  of  the  instrument,  by  making  the  two  sights  unequal 
by  the  same  amount  in  the  opposite  direction. 

On  ground  which  is  nearly  level  the  maximum  length  of  sight 
permissible  depends  on  the  state  of  the  atmosphere.  The  length  should 
not  be  so  great  that  the  image  of  the  target  in  the  telescope  appears 
to  "tremble"  or  "dance,"  due  to  currents  of  air  of  unequal  density 
between  the  instrument  and  target.  In  the  general  case  from  100  to 
200  yards  is  all  that  should  be  attempted  for  the  best  results.  On 
sloping  ground  the  sights  will  necessarily  be  short. 

When  the  height  of  the  trunnions  of  a  D.  P.  F.  instrument  is  required, 
a  scantling  or  board  straightedge  4  to  6  inches  in  width  may  be  placed 
on  edge  across  the  azimuth  table,  which  has  been  properly  leveled, 
taking  care  that  it  is  of  sufficient  length  to  project  through  a  window, 
door,  or  the  sighting  slit,  clear  of  the  tower  and  stairways.  In  order  to 
obtain  an  exit  through  the  sighting  slit,  it  may  be  necessary  to  lay  the 
straightedge  on  small  blocks  placed  on  the  azimuth  table.  In  any 
case  it  should  be  suitably  supported  to  prevent  flexure,  and  its  hori- 
zontality  secured  and  tested  by  a  carpenter's  or  machinist's  level. 
Note  the  height  of  the  axis  of  the  trunnions  above  its  datum  edge,  and 
by  means  of  a  steel  tape,  measure  the  height  of  the  latter  above  some 
staple  point  on  the  ground  or  concrete  foundation.  With  the  Y 
level  and  leveling  rod,  find  the  height  of  this  point  above  the 
bench  mark  as  before  described.  We  thus  have  all  the  data  for 
finding  the  height  of  the  D.P.F.  instrument  trunnions  above  mean 
low  water. 

Sometimes  it  may  be  found  convenient  to  mark  the  level  of  the  datum 
edge  on  the  outer  surface  or  some  auxiliary  portion  of  the  tower,  and 
then  find  the  height  of  this  mark  above  some  point  on  the  ground  by 
the  ordinary  principles  of  surveying.  A  line  of  levels  to  the  bench  will 
then  give  the  information  desired. 

In  the  case  of  guns,  a  knowledge  of  the  heights  of  their  trunnions 
when  in  a  firing  position  is  necessary  in  calculating  the  quadrant  eleva- 
tions. It  will  often  be  found  practicable  to  run  a  line  of  levels  direct 
from  the  bench  mark  to  the  gun,  the  last  position  of  the  instrument 
being  on  the  parapet  and  the  rod  resting  on  the  cap  square.  Deducting 
the  radius  of  the  cap  square  from  the  difference  of  level  thus  found,  we 
have  the  height  of  the  trunnions.  This  will  often  involve  zigzagging 
up  the  exterior  of  the  parapet,  or  running  a  line  of  levels  up  a  ramp, 
but  may  frequently  be  accomplished  by  running  the  line  over  a  gradual 


458 


THE   SERVICE   OF  COAST   ARTILLERY 


slope  to  a  point  at  some  distance  and  at  such  an  elevation  that  a  suitable 
view  of  the  rod  held  on  a  cap  square  may  be  obtained. 

In  some  cases  it  will  be  more  convenient  to  run  a  line  of  levels  to  a 
point  in  rear  of  the  guns,  and  thence  by  easy  stages  to  a  point  on  the 
loading  platform;  the  height  of  the  trunnions  above  the  same  being 
found  from  the  authorized  drawings  or  by  steel  tape  and  straightedge. 
This  operation  may  be  reversed  if  desired. 

Sometimes  it  will  be  practicable  to  set  up  the  Y  level,  either  with 
or  without  its  tripod,  at  a  point  on  the  superior  slope,  and  read  the  rod 
held  on  a  cap  square;  thus  obtaining  the  height  of  the  instrument  above 
the  cap  square.  This  horizontal  line  of  sight  may  be  transferred  to  a 
D.  P.  F.  station  or  other  structure,  or  to  a  tree  or  flagstaff,  the  height 
above  the  ground  of  the  point  thus  marked  being  measured  by  a  steel 
tape.  Knowing  the  radius  of  the  cap  square  and  running  a  line  of  levels 
to  the  bench,  we  have  all  the  data  for  finding  the  height  of  the  gun  trun- 
nions above  mean  low  water. 

Example. — Determine  height  of  trunnions  of  8"  B.  L.  R.  (barbette), 
above  mean  low  water. 


Station. 

Back  Sight  (Feet) 

Front  Sight  (Feet) 

Remarks. 

B.M.  XIV. 

8.923 

Above  mean  low  water. 

1 

3.429 

4.124 

2 

3.852 

0.886 

3 

8.201 

0.611 

4 

11  All 

0.726 

5 

9.654 

0.974 

45.481 

7.321 

7.321 

38.160     = 

Height  of  gun  trunnions  above  mean  low  water. 

HYDROGRAPHIC   SURVEYING 

In  some  of  our  harbors  it  becomes  desirable  to  determine  from  time 
to  time  the  changes  which  may  have  occurred  in  the  depth  or  position 
of  one  or  more  of  the  channels,  the  depths  in  certain  areas  outside 
the  channel,  changes  in  the  three  and  four-fathom  contours,  etc.  The 
following  indicates  in  outline  the  methods  to  be  followed  in  making  such 
a  survey. 

In  general  terms,  soundings  are  made  from  a  tug,  launch  or  open 


SEACOAST  ENGINEERING  459 

boat  at  various  points  over  the  area  in  question,  the  position  of  the 
boat  at  the  moment  of  making  the  sounding  being  determined  by 
triangulation  either  from  the  shore  or  the  boat.  The  position  may 
then  be  plotted  on  the  chart,  and  the  corresponding  depth  of  water, 
reduced  to  mean  low  water,  marked  thereon.  It  will  be  seen,  there- 
fore, that  such  a  survey  contemplates  the  previous  determination  and 
accurate  location  on  the  chart,  of  several  points  on  shore  which  are  to 
be  used  as  points  of  reference.  In  other  words,  it  contemplates  a 
shore  base  line,  and  a  certain  amount  of  triangulation. 

Soundings  are  made  at  regular  intervals,  determined  either  by 
time  or  distance,  on  straight  lines  over  which  the  boat  is  caused  to  pass, 
the  lines  being  parallel  or  approximately  so,  and  normal  to  the  general 
trend  of  the  shore.  These  lines  should  not  be  farther  apart  than  from 
75  to  150  yards,  and  may  be  as  much  nearer  as  the  progress  of  the  work 
shows  to  be  necessary,  according  to  nature  of  bottom  and  accuracy 
desired.  On  each  line  soundings  should  be  taken  at  distances  apart 
not  greater  than  the  interval  between  the  lines. 

If  the  survey  is  of  considerable  importance,  a  second  system  of 
lines  may  be  run  at  right  angles  to  the  first  and  the  accuracy  of  the  work 
checked  by  the  arrangement  of  interpolated  soundings  where  the  lines 
cross. 

The  keeping  of  the  boat  on  the  line  is  much  facilitated  by  the  use 
of  "ranges,"  that  is  by  two  signals  placed  on  the  line.  The  boat  is 
then  so  steered  as  to  keep  on  the  range  thus  pointed  out.  The 
signals  may  consist  of  two  poles  set  on  shore  at  a  suitable  distance  apart, 
or  one  pole  on  shore  and  a  buoy.  The  range  should  be  marked  for  each 
line  to  be  run.  When  buoys  are  to  be  used  for  the  above  or  any  other 
purpose,  their  positions  must  be  determined  and  plotted  on  the  chart 
• — in  short,  they  are  to  be  considered  simply  as  additional  points  in  the 
land  triangulation  scheme.  The  same  is,  of  course,  true  of  any  signals 
used  to  indicate  a  range. 

A  suitable  buoy  for  the  purpose  may  be  made  of  any  light  wood, 
6  to  12  inches  in  diameter  at  top,  from  3  to  5  or  6  feet  long,  tapering 
toward  the  bottom.  A  through  hole  bored  in  the  direction  of  its 
length  permits  the  insertion  and  wedging  of  a  flagstaff.  To  the  lower 
end  of  this  staff,  projecting  below  the  end  of  the  float,  is  attached  the 
buoy  rope.  Rocks  may  be  used  as  anchors.  Buoys,  of  course,  swing- 
somewhat  with  the  tide,  and  are  therefore  not  as  reliable  as  po'nts  on 
land. 


CHAPTER  XI 
CORDAGE 

Yarn  is  formed  by  twisting  together  several  fibers  of  hemp  or  other 
material  used.  A  number  of  yarns  or  threads  twisted  or  spun  together 
form  a  strand,  and  three  or  four  of  these  strands  form  a  rope. 

Rope  is  cord  more  than  one  inch  ifc\ circumference,  made  up  of  hemp 
or  other  fibrous  material  or  of  steel  or  other  metallic  wire. 
Hawser  is  a  term  applied  to  large  ropes. 

Ropes  are  ordinarily  composed  of  three  strands  laid  up  right-handed, 
so  that  when  a  strand  is  followed  away  from  the  observer  the  rotation 
will  be  clockwise  or  laid  up  with  the  sun.  Hawser-laid,  plain-laid  or 
right-hand  rope  is  laid  up  in  this  manner.  (PI.  38,  Fig.  1.) 

Shroud-laid  Rope  contains  four  strands,  usually  laid  up  right- 
handed  round  a  smaller  rope  called  a  heart  or  core.  (PL  38,  Fig.  2.) 

Cable-laid  Rope  contains  three  right-handed  ropes  of  three  strands 
each,  laid  up  left-handed  into  one.  (PL  38,  Fig.  3.) 

Wire  Rope  contains  a  number  of  wires  twisted  into  strands,  three  to 
six  of  which  are  laid  up  round  a  wire  or  hemp  core.  It  is  about  three 
times  as  strong  as  hemp  rope,  but  lacks  elasticity  and  is  difficult  to 
handle.  It  is  used  principally  for  permanent  standing  rigging. 

The  size  of  a  rope  is  expressed  in  inches  and  fractions  thereof,  and 
is  measured  on  the  circumference. 

Rope  is  either  tarred  or  untarred;  the  latter  is  usually  called  white. 
It  is  more  suitable  for  tackles  than  tarred,  as  there  is  less  waste  of  power 
due  to  stiffness.  Tarred  rope  is  more  desirable  if  exposed  to  moisture. 
Hawser-laid  rope  should  be  coiled  with  the  sun;  cable-laid  rope 
against  the  sun.  To  allow  a  free  circulation  of  air  large  ropes  should 
be  coiled  and  stored  on  skids.  Small  ropes  may  be  hung  on  pins  or 
hooks.  Rope  should  not  be  coiled  wet.  Coiled  rope  should  be  uncoiled 
at  least  once  a  year  and  stretched  out  in  the  sun  for  a  few  days. 

Spun  Yarn  is  made  by  twisting  together  loosely  two  or  more  tarred 
yarns. 

Marlin  is  two-stranded,  right-handed.  It  is  made  of  spun  yarn 
tightly  twisted.  It  is  harder  and  smoother  than  spun  yarn. 

460 


CORDAGE  461 

Hambroline  is  two-stranded,  right-handed;  roundline  three-stranded, 
right-handed.  Both  are  made  of  fine  left-handed  yarns. 

Houseline  is  three-stranded,  left-handed.  It  is  made  of  finer 
dressed  hemp  and  has  a  smoother  appearance  than  spun  yarn. 

Hemp  Fiber  is  obtained  from  the  hemp  plant.  Manila  fiber  is 
obtained  from  a  species  of  plantain.  Coir  fiber  is  obtained  from  the 
outer  husk  of  the  cocoanut. 

Right-handed  rope  is  coiled  clockwise.  In  uncoiling  a  new  hemp 
rope  pass  the  end  which  is  at  the  core  through  the  coil  to  the  opposite 
side  and  coil  it  down  against  its  lay  to  get  the  turns  out  without  kinking. 
Wire  ropes  should  be  coiled  like  a  figure  8,  which  enables  their  being 
uncoiled  without  kinking. 

To  stretch  a  rope,  lay  it  out  its  full  length  along  the  ground,  make 
fast  one  end  to  a  swivel-hook  block  secured  to  a  holdfast  which  is  clear 
of  the  ground;  connect  the  other  end  with  the  drum  of  a  capstan  or 
winch.  As  soon  as  the  capstan  is  worked  sufficiently  to  make  the  rope 
taut  it  will  begin  to  unlay  and  spin  the  block  around,  thus  taking  the 
twist  out  of  the  rope.  When  the  required  strain  has  been  attained  the 
rope  should  be  left  taut  for  an  hour  or  more  and  then  coiled  up.  In  this 
way  it  may  be  tested  for  strength  as  well  as  stretched.  (PL  38,  Fig.  4.) 

The  Safe  Load  which  can  be  put  on  a  rope  is  very  much  less  than 
the  breaking  weight.  It  should  not  exceed  one-third  of  the  standard 
breaking  weight,  and  when  using  a  worn  rope  or  with  live  loads  it  is 
necessary  to  use  a  larger  factor  of  safety.  Should  any  doubt  exist  as 
to  the  condition  of  the  rope  a  portion  of  it  should  be  actually  strained 
to  its  breaking  point,  and  the  proper  factor  of  safety  applied  to  the 
remainder,  or  the  whole  rope  that  is  to  be  used  tested  with  a  ten  per 
cent  greater  pull  than  the  proposed  working  load  to  be  put  on  it. 

The  breaking  weight  of  hemp  rope,  hawser-laid,  3-inch,  3-strand, 
tarred,  is  3  tons  per  fathom  (6  feet)  of  length.  Same  rope  white  4£ 
tons.  Manila  rope  hawser-laid  tarred  4^  tons.  Same  rope  white  4f 
tons.  Coir  rope  hawser-laid  white  7  tons.  Steel  wire  rope  17  tons. 

The  strength  of  other  sizes,  from  1  to  4  inches,  can  be  calculated 
from  this  on  the  principle  that  the  strength  varies  with  the  square 
of  the  circumference  of  the  rope.  Larger  sizes  than  4-inch  are  not 
quite  as  strong  in  proportion  to  their  size. 

The  strength  of  a  chain,  when  the  links  are  not  longer  than  5  times 
the  diameter  of  the  iron  is:  Mean  breaking  weight  in  tons  =24  times 
square  of  diameter  of  iron  in  inches. 

The  Bight  of  a  rope  is  any  part  not  an  end.  A  bight  is  a  loop  formed 
by  bending  or  doubling  the  rope. 


462  THE   SERVICE   OF  COAST  ARTILLERY 

The  Jaws  are  the  open  grooves  between  the  strands.  A  rope  is 
said  to  be  long-jawed  or  short-jawed  as  it  is  loosely  or  tightly  layed  up. 

The  Running  End  of  a  rope  is  the  free  end ;  and  the  rest  of  the  rope 
is  the  standing  part  or  end. 

Standing  Rigging  comprises  stationary  ropes  such  as  guys  for  sheers, 
stays  for  derricks,  etc.  Guys  are  made  fast  to  natural  or  artificial 
holdfasts.  (PI.  40,  Fig.  38.) 

Running  Rigging  comprises  ropes  running  through  blocks.  (PI.  39, 
Fig.  54.) 

Whipping  is  the  securing  of  the  end  of  a  rope  with  twine  to  prevent 
it  fraying  out  or  unlaying.  The  method  is  shown  in  Plate  38,  Figs. 
5,  6  and  7. 

Worming  is  filling  up  the  jaws  of  a  rope  by  laying  spun  yarn  or 
marlin  along  them  to  make  a  smooth  surface  for  parceling  or  worming. 
PI.  38,  Fig.  8a  shows  the  method. 

Parceling  is  wrapping,  with  the  lay  of  the  rope,  narrow  strips  of 
tarred  canvas  round  it  to  secure  it  from  injury  by  water;  also  to  prevent 
the  rope  from  being  chafed  or  cut  when  brought  against  a  rough  surface 
or  sharp  edge.  For  this  latter  purpose  old  rope  or  canvas  suffices. 
PI.  38,  Fig.  86,  shows  the  method. 

Serving  is  the  laying  on  tightly  of  spun  yarn  or  other  material 
in  turns  round  and  against  the  lay  of  the  rope.  A  serving  board  or 
mallet  is  used  to  draw  the  service  tight.  (PL  38,  Fig.  Sd.)  The  method 
is  shown  in  PL  38,  Fig.  8c. 

Splicing  is  joining  two  ends  of  a  rope  together,  or  joining  an  end 
to  any  part  of  it,  by  interweaving  the  strands  in  a  regular  manner. 
There  are  three  kinds  of  splices. 


SPLICES 

The  Short  Splice  is  used  to  connect  two  ends  of  rope  not  intended 
to  run  through  blocks. 

To  make  the  short  splice,  unlay  for  a  convenient  length  the  ends  of 
the  two  ropes  to  be  joined,  whip  the  strands  of  both  ropes  with  fine 
twine;  having  placed  each  of  the  strands  of  one  rope  opposite  to  and  in 
the  interval  between  the  corresponding  strands  of  the  other  exactly  as 
shown  in  PL  38,  Fig.  9:  draw  them  close  together,  now  hold  the  end 
of  one  rope  (the  left)  and  the  three  strands  which  come  from  the  opposite 
rope  firmly  in  the  left  hand,  or  if  the  rope  be  large  tie  the  strands  down 
with  marlin.  Take  the  middle  free  strand  and  pass  it  over  the  strand  of 


PLATE  XXXVIII 


1.  2.  3. 

PLAIN       SHROUD)  CABLE 

LAID  LAID  LAID 


STRETCHING 


WHIPPING 


7. 
"WHIPPING 


28.  29.         30.  31. 

THUMB  FIGURE-    STEVEDORE'S'     %  FLEMISH 
27 .  OF-EIGHT 

OVERHAND 


4V. 

RIGGING 


CORDAGE  463 

the  other  rope  next  to  the  left  of  it,  then  tuck  under  the  second  and  out 
between  the  second  and  third  strands  from  it,  then  haul  the  splice  taut. 
It  should  now  be  identical  with  PL  38,  Fig.  10.  Now  pass  each  of  the 
other  strands  in  the  same  manner,  first  those  of  one  rope  and  then  those 
of  the  other,  the  splice  assuming  the  appearance  of  PL  38,  Fig.  11. 
Continue  this  same  operation  until  the  strands  are  used  up — though 
three  tucks  of  the  strands  of  each  rope  are  usually  sufficient.  After 
the  ends  have  been  tucked  through  once,  a  neater  finish  may  be  obtained 
by  dividing  the  strands,  passing  one  half  of  each  for  the  second  tuck  as 
described  above  and  cutting  off  the  unused  half;  for  the  third  tuck 
repeat  the  halving  of  each  strand.  Finish  by  hauling  the  strands  well 
through  and  flatten  by  beating  with  a  marlinspike  or  mallet,  and  cut 
the  ends  of  strands  off  close  to  the  rope  and  whip  the  joints  with  twine. 

Grease  may  be  rubbed  in  the  strands  when  necessary  to  make  them 
flexible. 

A  tapering  pin  called  a  fid,  if  of  wood,  and  a  marlinspike  if  of  iron, 
should  be  used  to  open  the  span  between  strands  sufficient  for  the 
opposite  strand  to  be  pulled  through  in  each  case. 

The  Eye  Splice  is  used  to  form  an  eye  or  loop  in  a  rope.  It  is  made 
in  a  manner  similar  to  that  of  the  short  splice.  The  strands  are  unlaid 
as  far  as  may  be  judged  necessary  to  make  three  tucks.  (PL  38,  Fig.  12.} 
The  ends  of  the  center  and  left  strand  are  tucked  through  the  correspond- 
ing spaces  between  the  strands  of  the  standing  part  at  a  point  which 
will  make  an  eye  of  the  required  size.  (PL  38,  Fig.  13.)  The  splice 
is  then  turned  over  and  the  remaining  strand  is  tucked  under  and 
pointed  to  the  left  as  indicated  in  PL  38,  Fig.  14.  The  tucking  over 
and  under  is  then  continued  as  explained  for  the  short  splice. 

The  Long  Splice  is  made  to  join  ropes  intended  to  run  through  a 
block.  To  make  a  long  splice  unlay  the  ends  of  the  two  ropes  to  be 
joined  to  a  distance  three  or  four  times  as  great  as  for  a  short  splice 
and  place  them  together.  Unlay  one  strand  for  a  considerable  distance 
and  fill  up  the  interval  as  it  is  unlaid  writh  the  opposite  strand  of  the 
other  rope  following  it  up  closely  as  shown  in  PL  38,  Fig.  15.  Twist 
these  two  ends  together  as  shown  in  PL  38,  Fig.  16,  then  do  the  same 
with  two  more  strands,  untwisting  the  strands  in  the  opposite  direction 
from  that  of  the  first.  The  two  remaining  strands  are  twisted  together 
in  the  place  where  they  were  first  crossed.  Open  these  last  two  strands 
and  divide  each  in  two,  then  make  an  overhand  knot  with  the  opposite 
halves  and  lead  the  ends  over  the  next  strand  and  under  the  second  in 
the  same  manner  that  the  strands  were  passed  for  the  short  splice. 
Trim  off  the  two  halves.  Do  the  same  with  the  others  that  are  placed 


464  THE   SERVICE   OF  COAST  ARTILLERY 

together,  dividing,  knotting  and  passing  them  in  the  same  manner. 
Before  trimming  off  any  of  the  half  strands  the  rope  at  the  splice  should 
be  well  stretched.  Sometimes  the  whole  strands  are  knotted,  then 
divided  and  the  half  strands  passed  as  described. 

The  long  splice  is  from  15  to  40  per  cent,  weaker  at  the  splice  than 
the  rest  of  the  rope. 

Wire  Rope  is  spliced  in  a  somewhat  similar  manner  (PL  38,  Fig.  17). 
This  rope  is  usually  six-stranded  with  a  hemp  core.  The  three  alternate 
strands  of  each  of  the  parts  to  be  spliced  are  first  unlaid  to  a  distance 
of  about  nine  feet  and  then  cut;  the  hemp  core  is  also  removed  the 
same  distance;  the  rope  being  first  tightly  bound  with  wire  at  this 
point.  The  remaining  strands  are  then  unlaid  and  the  two  ropes 
placed  together  as  for  a  long  splice  so  that  the  cut  strands  abut. 

No.  1  cut  strand  of  one  rope  is  then  unlaid  and  the  corresponding 
strand  of  the  other  rope  is  laid  up  in  its  place  until  all  but  nine  inches 
of  the  latter  has  been  laid  up.  No.  2  strand  of  the  first  rope  is  then 
unlaid  and  its  place  is  filled  in  a  similar  manner  by  the  corresponding 
strand  of  the  other  rope  up  to  about  two  feet  from  where  the  first  two 
strands  met,  and  then  each  strand  is  cut  about  nine  inches  from  where 
they  meet.  In  this  manner  all  the  strands  are  laid  in,  first  those  on 
one  side  and  then  those  on  the  other,  the  distances  between  the  points 
where  the  different  ends  meet  being  about  two  feet,  and  the  whole 
splice  taking  up  about  ten  feet.  The  projecting  ends  of  the  strands 
are  then  laid  into  the  middle  of  the  rope  at  these  places,  the  rope  being 
partially  untwisted  to  enable  this  to  be  done,  and  enough  of  the  core 
being  removed  to  make  room  for  the  ends.  The  rope  is  then  twisted 
back  and  well  hammered  down  with  wooden  mallets,  and  when  the 
splice  has  been  properly  made  it  cannot  be  detected  after  the  rope  has 
been  running  for  a  day  or  two. 

An  Eye  Splice  in  wire  is  made  in  a  similar  manner  to  that  in  rope, 
but  in  view  of  the  difficulty  and  delay  involved  in  splicing  wire  rope,  the 
parts  are  often  fastened  together  by  means  of  screw  clamps  or  clips 
which  are  quickly  and  easily  applied  and  give  as  strong  a  connection 
as  a  splice. 

Pointing  is  the  operation  of  tapering  the  end  of  a  rope  so  that  it 
will  enter  a  hole  or  block  more  easily.  (PL  38,  Fig.  18,  19,  and  20.) 

Seizing  a  rope  is  to  lash  two  parts  of  it  together,  or  to  lash  two 
ropes  together,  by  means  of  spun  yarn,  seizing  stuff,  or  marlin,  as  shown 
in  PL  38,  Fig.  22,  c. 

Round  Seizing  is  when  the  seizing  material  is  wound  round  both 
ropes  without  passing  between  them  as  shown  in  PL  38,  Fig.  21. 


CORDAGE  465 

Racking  Seizing  is  when  the  seizing  material  is  wound  round  the 
ropes  in  figures  of  eight,  as  shown  in  PI.  38,  Fig.  22,  a. 

Nippering  is  the  binding  together  of  two  ropes^as  parts  of  a  block 
and  fall,  to  prevent  them  from  slipping  when  the  running  end  is  cast 
loose.  It  is  done  by  seizing  or  passing  a  loop  around  them  once  or 
twice  and  passing  a  spike  in  the  bight  and  twisting  it  as  shown ^in 
PL  38,  Fig.  22,  b. 

Mousing  a  hook  is  to  seize  the  point  and  back  to  strengthen  and 
prevent  it  from  disengaging  itself  from  anything  to  which  it  may  be 
hooked.  PL  38,  Figs.  23  and  24  show  the  method;  it  is  secured  by  a 
square  knot. 

Frapping  is  used  to  draw  two  ropes  and  hold  them  while  taking  up 
slack.  PL  38,  Fig.  25,  shows  the  method. 

Inside  Clinch  is  used  for  fastening  a  stiff  rope  to  a  ring  or  other 
object.  It  is  made  by  passing  the  ends  through  the  ring  or  round  the 
object,  leading  it  round  the  standing  part  and  through  the  bight, 
forming  a  circle;  a  seizing  is  then  put  on  the  circle  (sometimes  two 
seizings  are  put  on),  and  the  clinch  will  appear  as  in  PL  38,  Fig.  23. 

A  Strap  or  Sling  is  usually  made  of  rope  the  ends  of  which  are  either 
spliced  or  tied  together.  It  is  passed  round  the  object  to  be  moved, 
the  hook  of  the  tackle  being  passed  through  both  bights,  as  shown  in 
PL  39,  Fig.  42,  c,  or  through  one  bight  after  it  has  been  passed  through 
the  other  one. 

A  Stopper  is  a  short  piece  of  rope,  or  a  gasket  used  to  keep  any 
weight  suspended  or  to  take  the  strain  off  a  rope. 

Lashing  is  the  binding,  or  making  fast,  of  one  object  to  another  by 
means  of  ropes. 

Cleats  are  used  to  prevent  lashing  from  slipping,  made  by  cutting 
lengthwise,  diagonally,  a  piece  of  6X6  inch  scantling  2  feet  long. 

Anti-twisters  are  contrivances  employed  for  preventing  the  main 
tackle  and  guys  of  sheers  and  derricks  from  twisting.  They  are  made 
by  placing  a  handspike  or  smooth  picket  at  right  angles  between  the 
returns  as  close  to  the  moving  block  (or  block  that  rotates)  as  possible, 
the  handspike  being  kept  in  place  by  lashing  or  drag-rope  at  one  end. 
held  by  two  men  or  made  fast  to  a  fixed  object.  Another  method 
is  to  lash  a  handspike  or  capstan  bar  across  the  movable  or  rotating 
block,  with  a  rope  attached  to  either  end  of  the  handspike  and  held  or 
made  fast  as  before. 

A  Leading  Block  is  used  when  a  weight  is  to  be  raised  and  force 
cannot  be  applied  in  the  direction  in  which  it  would  be  most  effective. 
A  single  block  is  made  fast  at  some  point  so  as  to  lead  the  fall  in  the 


466  THE  SERVICE   OF  COAST  ARTILLERY 

direction  in  which  it  is  intended  that  the  weight  shall  be  hauled  upon. 
The  rope  is  passed  around  the  sheave  of  this  block  and  can  then  be 
hauled  in  the  m oak  convenient  direction. 


KNOTS 

Overhand  Knot. — PL  38,  Fig.  27,  shows  the  method  of  tying. 
When  drawn  up  tight  it  is  called  a  Thumb-knot. 

PI.  38,  Fig.  28. — Thumb-knot,  used  to  prevent  the  end  of  a  rope 
from  unlaying,  also  used  as  a  stopper  to  prevent  the  end  of  a  rope  from 
slipping  through  a  ring  or  eye. 

PI.  38,  Fig.  29.— Figure-of-eight  knot. 

PL  38,  Fig.  30.— Stevedore's  knot. 

PL  38,  Fig.  31.— Flemish  knot. 

PL  38,  Fig.  32.— Flemish  loop. 

PL  38,  Fig.  33.— Chain  knot. 

PL  38,  Fig.  34.— Square  or  reef  knot. 

PL  38,  Fig.  35.— Thief  knot. 

PL  38,  Fig.  36.— Granny  knot. 

PL  38,  Fig.  37. — Draw  knot.     It  is  untied  by  pulling  at  the  end,  a. 

PL  38,  Fig.  38.— Running  or  slip  knot. 

PL  38,  Figs.  39,  40  and  41.— A  bowline  knot. 

PL  38,  Fig.  42.— Running  bowline. 

PL  38,  Fig.  43  and  44.— Bowline  on  a  bight. 

PL  38,  Fig.  45. — Anchor  knot  or  fisherman's  bend. 

PL  38,  Fig.  46.— Prolonge  knot. 

PL  38.  Fig.  47.— Rigging  knot.  Used  to  attach  guys  to  a  derrick 
or  mast.  The  opening  is  placed  over  the  top  of  the  derrick  and  the 
four  guys  are  attached  to  the  ends  of  the  rope  h  and  i,  and  to  the  loops 
a  and  c.  * 

PL  38,  Fig.  48,  49,  and  50.— Single  wall  knot. 

PL  38,  Figs.  51  and  52. — Crowning  a  wall  knot.  Fig.  52  shows  the 
crown  at  the  top,  i.e.,  looking  down  the  rope. 

PL  38,  Figs.  53  to  59.— Double  wall  and  double  crown. 

PL  39,  Figs.  1,2,  and  3. — Single  and  double  diamond  knot. 

PL  39,  Fi  s.  4  to  7. — Matthew  Walker's  knot. 

PL  39,  Figs.  8  to  11.— Turk's-head.  The  method  used  to  insure 
it  from  slipping  is  shown  in  PL  39,  Fig.  12;  weave  the  ends  as  shown 
in  the  diamond  or  the  wall  knot. 

PL  39,  Figs.  13  and  14. — Single  bend,   sheet-bend,  single  becket  or 


CORDAGE  467 

weaver's  knot.  Used  for  joining  two  ropes  of  different  sizes  or  a  rope 
to  another  one  at  an  eye. 

PI.  39,  Fig.  15.— Double  bend  or  double  becket. 

PL  39,  Figs.  16  and  17. — Carrick  bend,  used  for  joining  a  hawser 
or  chain. 

PL  39,  Fig.  18.— Hawser  bend. 


HITCHES 

PL  39,  Fig.  19. — Half  hitch.  Made  by  passing  the  running  end,  a, 
of  a  rope  round  the  rope  or  spar  to  which  it  is  to  be  attached,  then  round 
the  standing  part,  6,  and  bringing  it  up  to  the  bight  c.  It  may  also  be 
seized  to  the  standing  part  at  d.  A  safe  rule  to  adopt  in  all  cases  where 
a  knot  is  likely  to  jam  or  become  untied  is  to  lash  the  free  end  to  the 
standing  part  as  shown  in  PL  39,  Fig.  38. 

PL  39,  Fig.  20.— Two  half  hitches.  Round  turn  and  two  half 
hitches.  Same  as  two  half  hitches  except  that  a  complete  turn  is  first 
taken  round  the  spar  or  other  object  to  which  the  rope  is  to  be  attached. 

PL  39,  Fig.  21. — Rolling  hitch.  Used  to  haul  a  spar  or  other 
object  in  the  direction  of  its  length. 

PL  39,  Figs.  22  to  25. — Clove  hitch,  sometimes  used  to  fasten  a 
small  boat  to  a  pile  or  a  heaving  line  to  a  cable.  In  the  latter  case  one 
or  two  half  hitches  should  be  taken  round  the  cable  with  the  free  end. 

PL  39,  Figs.  26  and  27. — Magnus  hitch,  or  mooring  knot.  Used  to 
fasten  a  mooring  rope  to  a  pile. 

PL  39,  Fig.  28  and  29. — Timber  hitch.  Used  to  secure  a  rope  tem- 
porarily to  a  spar  to  lift  or  haul  it. 

PL  39,  Fig.  30. — Marlinspike  hitch  or  lever  hitch.  Used  to  draw 
a  seizing  tight. 

PL  39,  Fig.  31.— Stopper  hitch. 

PL  39,  Fig.  32. — Telegraph  hitch.  Used  to  haul  a  smooth  spar  in 
the  direction  of  its  length. 

PL  39,  Fig.  33.— Blackwall  hitch. 

PL  39,  Fig.  34.— Midshipman's  hitch. 

PL  39,  Figs.  35  to  38.— Cat's  paw. 

PL  39,  Figs.  39  and  40. — Sheep  shank.  Used  to  shorten  a  rope 
without  cutting  it. 


468  THE  SERVICE   OF  COAST   ARTILLERY 


STRAPS,   ETC. 

PL  39,  Figs.  41  and  42. — Selvagee  made  by  planting  two  pickets 
or  pins  at  a  distance  apart  equal  to  the  intended  length;  wind  rope 
yarn  round  them  until  the  selvagee  is  thick  enough  for  the  purpose 
intended  and  then  bind  it  together  with  the  same  yarn,  half-hitched 
round  it  at  intervals  of  about 'an  inch.  The  method  of  applying  to  a 
rope  is  shown  in  PL  39,  Fig.  42. 

PL  39,  Figs.  43  to  46. — Gasket.  Is  made  of  rope  unstranded  and 
plaited. 

PL  39,  Figs.  47  and  48. — Sheer  lashing,  is  used  to  bind  together  the 
legs  of  sheers  in  such  a  way  that  the  lashing  will  not  slip  when  the 
weight  is  suspended  from  it.  The  legs  are  crossed  at  the  end  near 
where  the  lashing  is  to  be,  but  with  a  less  angle  between  them  than  the 
legs  will  have  when  the  sheers  will  be  in  position,  so  that  the  spreading 
of  the  legs  will  tighten  the  lashing.  Begin  with  a  clove  hitch  round 
one  leg,  then  pass  as  many  turns  round  both  legs  as  may  be  necessary, 
ending  with  two  or  three  frapping  turns  round  the  lashing  itself  and 
then  fast  n  the  end  by  two  half  hitches  round  one  leg. 

PL  39,  Figs.  49  and  50. — Barrel  or  cask  sling. 


BLOCKS  AND   TACKLES 

PL  39,  Fig.  51. — A  block  consists  of  four  parts:  the  shell  or  outside 
framework;  the  sheave  or  grooved  pulley  on  which  the  rope  runs;  the 
pin  or  axle  on  which  the  sheave  turns;  and  the  strap  (when  used),  made 
of  rope  or  iron,  which  encircles  the  shell  and  supports  the  hook  and  eye 
of  the  block. 

A  mortised  block  is  made  of  a  single  block  of  wood  mortised  (cut) 
to  receive  one  or  more  sheaves. 

PL  39,  Fig.  52. — Heavy  blocks  for  artillery  purposes  are  generally 
made  of  an  iron  or  steel  shell,  with  single,  double,  treble  or  fourfold 
brass  sheaves. 

'  The  size  of  a  block  is  expressed  by  the  length  of  the  shell  in  inches. 
A  running  block  is  attached  to  the  object  to  be  raised.  A  standing- 
block  is  fixed  to  the  support  or  holdfast.  A  leading  block  is  a  single 
standing  block  used  when  power  cannot  be  applied  directly. 

PL  39,  Fig.  53. — Snatch  block,  a  single  sheave  block  having  an 
opening  in  one  side  to  insert  the  bight  of  a  fall. 


PLATE    XXXIX 


50.  51. 

BARREL  MADE 

SLING  BLOCK 


Cordage,  etc. 


CORDAGE  469 

Tackle  is  a  purchase  formed  by  rigging  a  rope  through  one  or  more 
blocks  working  together. 

Purchase,  a  tackle  of  any  kind  for  gaining  power. 

Simple  tackle,  consists  of  one  or  more  blocks  rove  with  a  single  rope, 
or  fall.  (PL  39,  Fig.  54.) 

Standing  parts,  are  parts  of  the  rope  of  a  tackle  between  the  fasts 
and  a  sheave. 

Running  parts,  are  between  the  sheaves. 

The  fall  is  the  part  to  which  the  hauling  power  is  applied. 

PL  40,  Figs.  2,  3,  and  4.— Whip.  The  simplest  form  of  tackle;  it  is 
made  by  a  rope  rove  through  a  single  block. 

PL  40,  Fig.  5. — Whip  upon  whip,  so  called  where  the  block  of  one 
whip  is  attached  to  the  fall  of  another. 

PL  40,  Fig.  12. — Gun  tackle  is  made  by  reeving  a  rope  through 
two  single  blocks  and  making  the  standing  end  fast  to  the  upper  block. 

PL  40,  Fig.  14. — Luff  tackle  is  made  by  reeving  a  rope  through  a 
single  and  a  double  block.  Inverted  it  is  called  a  watch  or  tail  tackle. 

Luff  upon  luff.  A  luff  tackle  upon  the  fall  of  another  luff  tackle 
is  so  called. 

Gin  tackle  consists  usually  of  a  double  and  a  treble  block,  but  may 
consist  of  a  single  and  a  double  block. 

PL  40,  Fig.  17. — Single  Burton  consists  of  two  single  blocks  with 
the  fall  reeved  as  shown  in  the  figure. 

PL  40,  Fig.  18. — Double  Burton,  a  single  Burton  with  an  additional 
whip  attached  to  its  fall,  the  standing  part  of  which  is  also  attached  to 
the  weight  to  be  raised. 

PL  40,  Fig.  19. — Spanish  Burton,  a  gun  tackle  with  a  whip  attached 
to  its  fall. 

PL  40,  Fig.  20.— Double  Spanish  Burton,  a  luff  tackle  with  a  whip 
attached  to  its  fall  in  the  same  manner  as  a  Spanish  Burton. 

POWER   OF   TACKLE 

The  actual  power  of  any  tackle  may  be  approximately  calculated 
from  the  theoretical  power.  In  obtaining  the  latter  it  is  assumed  the 
rope  or  cord  used  is  perfectly  flexible,  not  elastic,  and  that  the  blocks 
have  no  friction.  It  is  obviously  impossible  to  find  such  a  condition  in 
practice.  By  the  power  of  a  tackle  is  meant  the  ratio  of  the  force 
exerted  by  it  to  that  applied  to  the  fall.  This  should,  more  strictly 
speaking,  be  termed  force,  and  not  power,  as  force  is  that  which  is 
gained  by  a  tackle. 


470  THE   SERVICE   OF   COAST  ARTILLERY 

If  a  weight  W,  equal  to  P  pounds,  is  suspended  from  one  end  of  a 
perfectly  flexible  and  inextensible  cord  passing  over  any  number  of 
frictionless  pulleys,  a  pull  equal  to  P  pounds  will  have  to  be  exerted  at 
the  other  end  of  the  cord  to  support  this  weight,  and  every  intermediate 
portion  of  the  cord  will  have  a  pull  upon  it  equal  to  P  pounds,  which  is 
exerted  in  the  direction  of  the  cord.  See  PL  40,  Fig.  1.  This  is  the 
fundamental  principle  of  the  theoretical  power  of  any  tackle. 

The  theoretical  powers  of  the  various  tackles  illustrated  in  PL  40, 
Figs.  1  to  20  inclusive,  are  shown  on  the  figures  themselves.  A  simple 
rule  of  obtaining  the  gaining  power  of  any  tackle  is  that  the  force  applied 
multiplied  by  the  number  of  moving  parts  is  equal  to  the  power  gained. 
For  example,  PL  40,  Fig.  15,  shows  one  standing  part  (i.e.,  the  part 
attached  from  the  hook  of  the  upper  block  to  the  sheave  of  the  lower 
block),  and  four  running  parts;  accordingly  the  power  gained  for 
hoisting  is  four.  The  tackle  inverted  would  give  a  power  of  five,  for 
the  reason  in  that  case  the  upper  part  moves,  increasing  the  number 
of  running  parts  by  one. 


LEVERS 

The  three  orders  of  levers  are  shown  in  PL  40,  Figs.  22  to  29,  called 
respectively  lever  of  the  first  class,  second  class,  and  third  class.  The 
classification  depends  entirely  on  the  position  of  the  fulcrum  or  prop. 
The  fundamental  equation  of  these  classes  of  levers,  under  the  supposi- 
tion that  the  lever  is  straight  and  that  the  weight  W  and  force  F  act 
at  right-angles  to  it,  is  as  follows:  lever  arm  L  is  equal  to  the  weight 

Wy.Cl 

W  times  its  lever  arm  Cl  or  the  counter-lever  arm;  or  F  = -. 

L 

When  levers  are  such  that  the  weight  and  force  do  not  act  at  right 
angles  to  the  lever,  the  perpendicular  distances  from  the  fulcrum  to  the 
lines  of  application  of  the  force  and  weight,  as  shown  in  PL  40,  Figs. 
24,  26,  and  27,  are  taken  as  the  lever  and  counter-lever  arms.  Taking 
such  distances,  the  above  formula  holds  good,  but  it  must  be  remembered 
that  in  using  a  lever  of  this  kind  the  lever  arm  and  the  counter-lever 
arm  do  not  usually  remain  constant,  but  change  in  might  as  the  lever 
is  moved  and  the  direction  of  the  applied  force  changes  with  respect  to 
the  lever,  see  PL  40,  Fig.  28. 

The  gaining  power  or  mechanical  advantage  of  a  simple  lever  is 

equal  to  -—   and   that,  of    a   double    compound    lever    is    equal    to 


PLATE  XL 


37. (b. ) 


Cordage,  etc. 


CORDAGE  471 

L      U 

—  X—  in  which  L  and  L',  Cl   and  Cl'  pertain  to   the   corresponding 

v>  L        v> ' 

parts  of  the  two  levers,  see  PL  40,  Fig.  29. 

An  example  of  the  lever  of  the  second  class  is  shown  by  the  gun 
represented  in  PI.  40,  Fig.  30.  The  gun  is  resting  on  two  supports, 
the  blocking  in  front  of  the  trunnions  representing  the  fulcrum 
and  the  jack  under  the  breech  representing  the  applied  force;  the 
weight  supported  by  the  jack  as  well  as  that  supported  by  the 
blocking  can  readily  be  determined  as  follows:  TF=30  tons,  L  or  ac 
in  the  figure  =227  inches,  d  or  ab  =  H2  inches,  therefore  the  applied 

30  V 1 12 
force  or  the  weight  supported  by  the  jack=— =14+  tons,  and 

_  _  i 

OQ  N/  1  1  5 

the  weight  supported  by  the  blocking  equals  =15+  tons. 


REVOLVING   LEVERS 

The  three  classes  of  revolving  levers  are  shown  in  PL  40,  Figs.  31, 
32,  and  33.  The  principle  of  these  levers  is  exactly  the  same  as  that 
enumerated  in  the  foregoing  cases.  The  lengths  of  the  lever  and 
counter-lever  arms  are  in  this  case  the  respective  radii  of  the  two 
circles.  This  variety  of  levers  is  exemplified  in  the  windlass  of  a  gin,  PL 
40,  Fig.  35;  the  capstan,  PL  40,  Fig.  46;  and  the  crab,  PL  40,  Fig.  47. 


DIFFERENTIAL   PULLEY 

The  differential  pulley  embodies  the  principles  of  the  revolving  lever, 
combined  with  that  of  a  single  movable  block.  .  It  consists  essentially 
of  two  iron  pulleys  of  unequal  diameter  mounted  upon  a  common  axle 
and  rigidly  attached  to  each  other;  an  endless  chain  passes  round  the 
larger  pulley  A  (PL  40,  Fig.  34),  down  round'  the  movable  pulley  B 
and  up  round  the  smaller  pulley  mounted  on  the  same  axle  with  A. 
The  upper  pulleys  are  sprocket  wheels  in  order  to  prevent  the  slipping  of 
the  chain.  Weight  is  suspended  from  the  lower  pulley  and  the  force 
is  applied  to  the  chain  at  P.  An  example  of  the  power  gained  by  the 
tackle,  neglecting  friction,  is  as  follows:  If  the  radius  of  the  larger  pulley 
is  6  inches,  and  the  small  pulley  5  inches,  the  power  of  the  tackle  will  be 

/-» 

12,  and  if  W  equals  1200  Ibs.,  F  would  equal  100  Ibs.,  or  2  .      -  -12. 

6—5 


472  THE   SERVICE   OF  COAST   ARTILLERY 


GINS,   ETC. 

The  mechanical  appliances  employed  in  fortifications  for  raising 
weights  are  Gins,  Sheers,  Derricks  and  Cranes.  In  each  case  the 
weight  is  raised  by  means  of  a  tackle,  either  alone  or  in  combination 
with  a  Capstan,  Crab,  or  the  Drum  of  a  hoisting  engine.  To  raise 
excessive  weights  the  Hydraulic  Jack  is  used  in  combination  with 
suitable  crib  work  built  up  of  wooden  blocks. 

A  Gin  is  represented  in  PL  40,  Fig.  35.  The  two  poles  supporting 
the  windlass  are  called  legs,  while  the  third  is  called  the  pry-pole,  and  is 
joined  with  the  others  at  the  head  by  a  bolt  which  also  supports  a  clevis 
to  which  the  upper  block  of  the  tackle  is  hooked.  The  windlass  is 
turned  by  two  metal  handspikes  which  fit  into  brass  sockets  at  each  end. 
Two  pawls  acting  on  ratchets  at  the  ends  of  the  windlass  keep  it  from 
turning  backward. 

Shoes  consisting  of  wooden  blocks  are  placed  under  the  lower  ends 
of  the  two  legs  and  pry-pole  called  the  feet,  to  keep  them  from  sinking 
into  the  ground.  That  part  included  between  the  legs  and  pry-pole 
after  the  gin  is  raised,  is  called  the  inside;  the  right  and  left  sides  are 
the  corresponding  right  and  left  sides  of  a  man  standing  behind  the  gin 
and  facing  it. 

The  tackle  for  hoisting  is  usually  a  double  and  treble  block  with 
fall  led  to  the  windlass  over  which  it  is  wound  two  or  more  times 
to  keep  it  from  slipping,  the  slack  of  the  rope  being  taken  up  by  hand  as 
the  windlass  revolves.  The  feet  should  be  as  nearly  as  possible  at  equal 
distances  from  each  other  and  on  the  same  level,  in  order  that  the 
weight  may  be  evenly  distributed  on  the  three  supports.  This  is 
essential  when  the  maximum  weight  for  which  the  gin  is  designed  is  to 
be  raised.  A  garrison  gin,  if  perfectly  sound,  is  capable  of  sustaining  a 
weight  of  17,000  Ibs. 

The  detachment  required  to  put  the  gin  together  and  handle  it  with 
facility  is  composed  of  one  chief  of  detachment,  one  gunner  and  ten 
privates.  The  post  of  the  chief  is  in  rear  of  the  gin,  but  he  goes  wherever 
his  presence  is  necessary.  The  gunner  is  on  the  left  side  near  the  head. 
The  odd  numbers  are  on  the  right,  and  the  even  numbers  on  the  left  side 
and  facing  the  gin.  PI.  40,  Fig.  36,  shows  their  relative  positions.  The 
chief  of  detachment  superintends  the  placing  of  the  windlass,  and  the 
gunner  the  putting  together  of  the  head ;  assisted  by  the  most  expert 
privates,  he  reeves  the  fall,  slings  the  gun  or  weight  to  be  raised  and 
attends  to  all  knottings  and  lashings. 

The  fall  is  either  reeved  on  the  ground  and  the  upper  block  then 


CORDAGE  473 

hoisted  up  to  its  position  by  means  of  a  rope  passing  over  the  clevis;  or 
after  the  gin  is  only  partly  raised  the  upper  block  is  hooked  to  the  clevis 
and  the  lower  block  to  the  middle  brace,  where  it  is  held  in  the  proper 
position  for  reeving.  The  fall  is  then  reeved  by  the  gunner  passing 
the  end  of  the  fall  through  the  left  sheave  of  the  upper  block  from 
without  to  within,  after  which  it  is  passed  through  the  sheave  of  the 
lower  block  from  within  to  without,  then  up  and  through  the  upper 
sheave  of  the  upper  block  in  the  same  direction  as  the  first  time  and  the 
end  then  made  fast  to  the  lower  block.  With  a  treble  upper  block  it  is 
preferable  to  pass  the  rope  through  the  middle  sheave  first,  as  it  will 
then  lead  better. 

Usually  the  gin  is  raised  t  after  being  put  together,  by  raising  the 
head  and  bringing  up  the  foot  of  the  pry-pole  towards  the  foot  of  the 
leg.  To  raise  the  gin,  Nos.  1  and  2  take  hold  of  the  pry-pole;  Nos.  9 
and  10  each  hold  down  the  foot  of  a  leg  to  keep  it  from  slipping;  Nos. 
3  and  4  remain  at  the  head,  and  Nos.  5,  6,  7  and  8  apply  themselves  to 
the  legs  on  their  respective  sides.  The  gunner  commands,  Heave,  and 
the  gin  is  raised ;  shoes  being  placed  under  the  pry-pole  and  each  leg. 

To  move  the  gin  after  it  has  been  raised,  Nos.  1  and  2  apply  them- 
selves to  the  pry -pole;  Nos.  9  and  10  each  place  a  handspike  under  the 
windlass  from  without  and  near  the  legs  and  assisted  by  Nos.  7  and  8 
from  within,  they  lift  and  move  the  gin  in  the  direction  indicated. 

The  gin  is  lowered  and  dismantled  by  the  reverse  operations  pre- 
scribed in  the  foregoing. 

A  Gin  Derrick  is  represented  in  PI.  40,  Fig.  37  (a  and  6).  It  is  a 
light  gin  equipped  with  a  gearing  for  operating  the  windlass.  It  is 
operated  like  other  gins  except  that  the  power  is  applied  to  the  wheels 
instead  of  to  the  handspikes. 

Sheers  are  represented  in  PI.  40,  Fig.  38.  They  are  composed  of 
two  legs  of  suitable  size.  The  upper  end  is  called  the  head,  the  lower 
end  the  heel  and  the  part  where  they  are  lashed  together  (as  shown  in 
PL  39,  Fig.  48)  the  cross.  A  gin  may  be  used  as  sheers  by  removing  the 
pry-pole,  replacing  it  by  a  short  block  of  wood  of  equal  thickness,  and 
attaching  the  guy  ropes.  Sheers  are  used  for  lifting  heavy  weights 
over  a  wall,  and  for  loading  and  unloading  guns,  etc. 

The  following  table  gives  the  approximate  size  and  length  of  spars 
required. 

Weight  to  be  Raised.  Mean  Diameter.  Length. 

3  to    5  tons  11  to  13  inches  30  to  40  feet 

5  to  12     "  13  to  16      "  40  to  50    " 

12  to  25     "  16  to  20      "  50  to  60    " 


474  THE  SERVICE   OF   COAST  ARTILLERY 

In  some  sheers  the  legs  are  connected  by  a  bolt  through  the  head  ? 
as  shown  in  PL  40,  Fig.  38,  instead  of  being  lashed  together  as  in  PL 
39,  Fig.  47. 

The  materials  necessary  to  equip  a  pair  of  sheers  are : 

Gun  Tackle. — Two  single  and  two  double  blocks. 

Main  Tackle. — One  double,  one  treble  and  one  snatch  block. 

Cordage. — Main  tackle  fall,  100  fathoms  (a  fathom  is  a  measure  of 
6  feet)  of  3-  to  5-inch  manila  rope;  guys,  100  fathoms  of  3-  to  6-inch 
manila  rope;  head  lashing,  10  fathoms  of  3- to  4-inch  manila  rope; 
heel  lashing  (two  each),  10  fathoms  of  3- to  4-inch  manila  rope;  con- 
tingencies, 50  fathoms  of  3-  to  4-inch  manila  rope. 

Straps. — Main  tackle,  one  fathom  long,  of  6-inch  manila  rope; 
snatch  block,  one  fathom  long,  of  4-inch  manila  rope;  guys  (two), 
each  one  fathom  long,  of  4-inch  manila  rope;  holdfasts  (six),  each  one 
fathom  long,  of  4-inch  manila  rope;  contingencies  (six),  each  a  half 
fathom  long,  of  4-inch  manila  rope. 

Spun-yarn  for  mousing,  stoppering,  etc.,  one  ball  of  100  fathoms. 
Two  cleats,  to  be  spiked  to  the  heels  about  6  inches  from  the  bottom. 
Stakes  for  holdfasts  and  heel  posts;  two  shoes  for  heels  or  one  long 
shoe  joining  the  two  heels  as  in  PL  40,  Fig.  38. 


TO    RIG   THE    SHEERS 

To  rig  the  sheers,  PL  39,  Fig.  48,  lay  the  heads  of  the  spars  on  a 
trestle  about  three  feet  high,  so  that  they  cross  at  about  twice  their 
thickness  from  the  upper  ends,  with  the  heels  in  the  proper  positions 
and  the  distance  from  the  cross  to  each  heel  exactly  the  same.  Make 
the  sheer  lashing,  as  previously  described;  or,  if  a  very  heavy  weight  is 
to  be  raised,  as  follows: 

Take  a  good  piece  of  3-  or  4-inch  rope,  well  stretched,  middle 
it  and  make  fast  to  one  of  the  legs  below  the  cross;  with  one  end  pass 
the  requisite  number  of  racking  seizing  turns  (PL  38,  Fig.  21)  round 
both  spars,  hauling  each  one  taut,  and  hitch  the  end  to  the  upper  end 
of  the  sheer-leg;  with  the  other  end  pass  round-seizing  turns  round 
both  spars,  filling  up  the  spaces  between  the  ropes  of  the  first  turns, 
as  far  up  as  the  first  rope,  and  pass  f rapping  turns  round  all  the  parts  of 
the  lashing  between  the  sheers ;  finish  with  a  square  knot  and  seize  the 
ends  with  spun  yarn.  If  necessary  tighten  up  the  lashing  with  wedges. 

A  guy  strap  having  the  splice  in  the  center,  so  that  the  splice  cannot 
come  into  either  bight,  is  then  laid  between  the  spars  above  the  cross 


CORDAGE  475 

and  equally  divided,  each  end  led  round  the  spar  farthest  away  from 
the  guy  for  which  it  is  intended,  the  ends  brought  back  round  both 
spars,  for  the  upper  guy  block  to  be  hooked  to,  or  the  guy  rope  itself 
is  attached  to  the  guy  strap.  The  other  guy  strap  is  put  on  in  the  same 
manner,  the  strain  on  each  guy  thus  tending  to  bind  the  spars  together. 

The  main  tackle  sling  is  then  put  on  over  the  cross  from  front  to 
rear,  passing  over  the  guy  straps  and  under  the  bights  for  the  headblocks 
(PL  39,  Fig.  48.)  The  upper  block  of  the  main  tackle  is  then  hooked 
through  both  bights  of  the  main  sling  and  the  hook  moused. 

Sink  or  lash  the  shoes  in  proper  positions.  They  must  be  on  the  same 
level,  and,  in  bad  ground,  prevented  from  sinking  or  slipping  by  placing 
planks,  brushwood  or  timber  underneath,  securing  them  by  pickets. 
Pickets  are  then  driven  as  holdfasts  for  the  foot  ropes;  for  the  lighter 
sheers,  two  for  each  foot,  one  in  front  and  one  in  rear  of  the  shoes,  so 
as  to  be  just  inside  the  heels  of  the  legs  when  they  are  on  the  ground  and 
a  few  feet  to  the  front  and  rear  of  the  shoes.  For  the  heavier  sheers 
four  are  required  for  each  foot.  Make  a  clove-hitch  with  the  middle  of  a 
foot  rope  round  each  leg  below  the  cleats  and  lead  the  ends  to  opposite 
holdfasts  where  they  are  made  fast. 

Put  down  the  holdfasts  for  the  rear  and  front  guys.  The  kind  of 
holdfasts  to  be  used  will  depend  upon  the  strain  on  them,  the  nature  of 
the  ground,  etc.  Those  shown  in  PL  40,  Figs.  39,  40,  41,  or  some 
modification  of  them,  will  generally  be  used,  but  sometimes  the  holdfast 
for  the  rear  guy  will  have  to  be  sunk  in  the  ground  as  in  PL  40,  Fig.  42,  to 
obtain  a  firm  hold.  Care  must  be  taken  to  have  both  holdfasts  on  the 
line  FG  (PL  40,  Fig.  44)  perpendicular  to  the  line  joining  the  heels  of 
the  sheers  at  its  middle  point. 

Hook  the  upper  blocks  of  the  guy  tackles  to  a  bowline  in  the  end  of 
the  guys,  or  to  the  guy  straps,  and  the  lower  blocks  to  the  holdfast 
straps,  and  mouse  all  the  hooks.  Ordinarily  the  fore  guy  can  be  worked 
without  a  tackle,  belaying  it  over  the  holdfasts,  first  taking  a  round  turn 
over  the  next  one  to  the  sheers,  but  if  the  sheers  have  to  be  inclined  to 
the  rear  with  the  weight  on  them,  the  front  guy  should  also  be  provided 
with  a  tackle,  and  be  as  carefully  secured  as  the  rear  guy. 

If  the  sheers  are  not  too  heavy  they  may  be  raised  by  lifting  the  head 
and  hauling  on  the  proper  guy  tackle,  slacking  the  heel  lashings  as 
required,  and  tending  the  opposite  guy  carefully  to  prevent  the  sheers 
from  falling  over  after  passing  the  vertical. 

If  the  sheers  are  too  heavy  to  raise  in  this  way,  form  a  crutch  by 
lashing  together  two  poles,  or  the  legs  of  a  gin,  near  their  upper  ends, 
the  feet  of  the  crutch  being  slightly  in  rear  of  the  heels  of  the  sheers  and 


476  THE  SERVICE   OF  COAST  ARTILLERY 

temporarily  secured  to  prevent  them  from  slipping.  Lay  the  rear 
guy  over  the  crutch  and  raise  the  crutch  by  means  of  two  light  guy 
ropes  until  it  is  inclined  at  an  angle  of  about  45  degrees  to  the  front. 
Haul  on  the  rear  sheer  guy,  allowing  the  crutch  to  rise  as  the  sheers  rise. 
After  the  sheers  are  raised  high  enough  so  that  the  crutch  ceases  to  act 
it  is  lowered  by  means  of  its  guy  ropes.  In  general,  the  inclination  or 
rake  of  the  sheers  should  not  exceed  20  degrees,  or  four-elevenths  of 
their  height.  In  this  position  the  pull  on  the  guy  will  not  exceed  one- 
half  the  weight.  An  allowance  of  7  or  8  degrees  in  the  rake  should  be 
made  for  the  stretch  of  the  guys. 

After  the  sheers  are  raised  hook  the  snatch  block  to  a  strap  placed 
below  the  cleat  on  one  of  the  legs,  or  to  a  holdfast  placed  in  a  convenient 
position. 

PL  40,  Fig.  44,  represents  in  plan  the  position  of  the  sheers,  holdfast, 
etc 

AD,  BC  are  the  legs  of  the  sheers. 

F,  the  front  guy  holdfast. 

G,  the  rear  guy  holdfast. 

E,  the  center  of  the  line  AB  at  right  angles  to  FG. 

AC=BC. 

The  splay  AB  =  J  CE. 

EF  and  EG=at  least  2  AC. 


DERRICKS   AND    CRANES 

Derricks  are  of  two  kinds,  standing  and  swinging. 

A  Standing  Derrick  (PL  40,  Fig.  21)  consists  of  a  single  spar  and 
is  used  when  a  direct  lift  or  slight  lateral  movement  is  required.  The 
spar  rests  on  a  shoe  and  is  supported  in  a  vertical  or  slightly  inclined 
position  by  three  or  four  guys  attached  to  the  head,  making  equal 
Tingles  with  each  other  and  secured  at  distances,  from  the  foot  of  the 
derrick,  of  at  least  twice  the  length  of  the  derrick.  The  strap  for 
supporting  the  hoisting  tackle  rests  in  a  groove  cut  in  the  top  of  the 
spar.  The  guy  blocks  are  lashed  to  the  head  of  the  derrick,  the  lashing 
passing  over  the  strap  for  the  hoisting  tackle,  binding  it  to  the  spar. 
Foot  tackles  are  used  to  prevent  the  derrick  from  slipping  and  a  snatch 
block,  lashed  with  a  cleat,  is  secured  at  the  foot  through  which  to  lead 
the  fall  from  the  hoisting  tackle.  The  top  of  the  spar  can  be  moved  a 
limited  distance  by  slacking  or  hauling  in  on  the  proper  guys,  and  in 
this  way  the  weight  moved  laterally. 


CORDAGE  477 

A  Swinging  Derrick,  as  shown  in  PL  40,  Fig.  43,  consists  of  two 
spars,  i.e.,  an  upright  called  the  mast,  and  a  swinging  spar  attached  to 
the  mast  near  its  base,  called  a  boom.  With  this  derrick  a  weight 
cannot  only  be  raised  and  lowered,  but  swung  in  a  circle,  of  which  the 
base  of  the  mast  is  the  center,  and  also  moved  in  and  out  from  the  mast 
a  distance  limited  by  the  length  of  the  boom.  The  mast  is  held  in  a 
vertical  position  by  three  or  four  guy  ropes.  Wire  ropes  fastened  to  a 
collar  on  the  top  of  the  mast  are  usually  used  when  the  derrick  is  to 
remain  erected  for  some  time.  The  method  of  supporting  the  boom, 
etc.,  is  shown  in  PL  40,  Fig.  43,  the  fall  being  led  to  the  drum  of  a  hoisting 
engine  or  to  a  capstan  or  crab.  For  steadying  the  weight  and  moving 
it  laterally,  two  smaller  guy  ropes  are  usually  fastened  to  the  weight  or 
to  the  block  supporting  it. 

A  Temporary  Swinging  Derrick  may  be  rigged  up  by  lashing  the 
guys  and  fastening  the  lower  end  of  the  boom  to  the  mast  by  a  rope  sling, 
and  lashing  the  necessary  blocks  to  the  upper  end  of  the  boom  and 
mast  to  support  the  boom  and  the  weight. 

For  steadying  the  weight  and  moving  it  laterally  two  smaller 
guy  ropes  are  usually  fastened  to  the  weight  or  to  the  block 
supporting  it. 

The  same  precautions  should  be  taken  in  erecting  a  derrick  and 
handling  a  weight  with  it  as  in  operating  with  sheers. 

To  ascertain  the  pull  on  the  guys  and  thrust  on  the  spars  of  sheers 
and  derricks. — Construct  on  paper  or  on  the  ground  a  diagram  similar 
to  PL  40,  Fig.  45. 

AD  to  represent  a  vertical  line. 

AB  the  inclination  of  the  sheers  when  supporting  the  weight. 

AC  the  inclination  of  the  guys. 

With  a  scale  of  equal  parts  (as  large  as  can  be  conveniently  used) 
lay  off  on  the  line  AD,  from  A,  a  distance  equal  to  the  number  of  units 
of  weight;  through  the  point  E  thus  found  draw  EF  parallel  to  AC'  until 
it  cuts  AB  at  F.  Then  the  distance  EF  measured  by  the  same  scale  will 
represent  the  pull  on  the  guy  and  AF  the  thrust  on  the  spars.  If  there 
are  two  spars  the  thrust  on  each  one  will  evidently  be  one-half  of  this, 
or  rather  a  little  more  than  one-half,  depending  on  the  angle  which  they 
make  with  each  other. 

It  must  be  borne  in  mind  that  the  thrust  on  the  sheers  is  not  only 
that  due  to  the  weight  lifted,  but  in  addition  to  this  the  amount  of 
pull  on  the  end  of  the  fall  required  to  support  this  weight  (see  PL  40, 
Figs.  12,  13,  and  14). 

A  Crane  differs  but  slightly  from  a  derrick  and  is  used  for  the  same 


478  THE  SERVICE   OF  COAST  ARTILLERY 

purpose,  being  usually  supported  by  braces  and  tie  rods,  when  necessary, 
instead  of  by  guys. 

Light  cranes  are  used  in  many  of  the  gun  emplacements  to  lift 
projectiles  up  to  the  loading  platform  and,  in  case  of  the  larger  barbette 
non-disappearing  carriages,  from  this  platform  to  the  breech  of  the  gun. 

A  Capstan  (PL  40,  Fig.  46),  is  a  machine  used  as  a  strong  purchase 
for  heaving  or  hoisting.  When  so  employed  it  is  held  in  position  by 
strong  ropes  or  chains  attached  to  holdfasts.  The  rope  is  passed  two 
or  three  times  round  the  barrel  of  the  capstan,  the  free  end  coming  off 
above  the  turns,  and  the  standing  part  being  attached  to  the  weight 
to  be  moved.  The  capstan  bars  are  inserted  in  mortises  in  the  head  of 
the  capstan,  and  the  free  end  of  the  rope  is  held  and  taken  in  by  two 
men  seated  on  the  ground. 

Twelve  men,  three  at  each  bar,  are  all  that  can  be  advantageously 
employed.  When  additional  power  is  required,  the  bars  are  swifted, 
that  is,  the  outer  ends  of  the  bars  are  joined  by  a  rope  lashed  to  each 
bar  for  additional  men  to  take  hold  of.  In  some  cases  horse  power  is 
used. 

A  Crab  (PL  40,  Fig.  47)  is  used  for  the  same  purpose  as  a  capstan; 
but  with  this  machine  the  force  it  applied  to  two  winches  and  power  is 
gained  by  the  operation  of  smaller  cog  wheels  upon  larger  ones;  it  being 
a  compound  revolving  lever. 

The  Sling-cart  is  used  for  moving  guns,  or  other  heavy  objects,  short 
distances.  There  are  two  kinds:  The  garrison  sling-cart  (PL  40,  Fig. 
48),  for  the  heaviest  weights,  is  attached  by  its  pole  to  a  limber,  and 
may  be  drawn  by  horses;  the  hand  sling-cart  is  designed  for  moving 
lighter  weights  by  hand. 

With  the  hand  sling-cart  the  weight  is  raised  sufficiently  from  the 
ground  to  transport  it  by  first  attaching  a  sling  of  the  proper  length  to 
the  weight  to  be  moved  and  then  raising  the  pole  of  the  cart  enough  to 
permit  the  hook  on  the  rear  of  the  axle  being  hooked  into  this  sling. 
The  pole  in  this  case  is  used  as  a  lever,  the  axle  and  wheels  being  the 
fulcrum,  and  the  weight  is  raised  by  lowering  the  end  of  the  pole.  It 
may  be  used  for  transporting  any  weight  up  to  6,000  pounds. 

With  the  garrison  sling-cart  the  weight  is  raised  by  first  attaching  it 
to  a  sling,  and  then  applying  the  sling  to  the  hooks  forming  the  lower 
part  of  a  powerful  screw  passing  up  through  the  axle  of  the  cart.  Above 
the  axle  is  the  butt  of  the  screw,  provided  with  long  handles  by  means 
of  which  the  screw  is  run  up,  thus  raising  the  weight. 

This  sling-cart  is  capable  of  supporting  20,000  pounds;  but  as  with 
such  heavy  weights  it  is  difficult  to  turn  the  handles  of  the  screw  to 


CORDAGE  479 

raise  it;  the  cart  has  been  modified  by  substituting  a  hydraulic  jack 
for  the  screw. 

A  Sling-wagon  (PL  40,  Fig.  49)  is  also  provided  for  moving  guns 
or  heavy  material.  In  this  the  weight  is  raised  by  means  of  a  hydraulic 
jack,  and  supported  by  pins  through  the  vertical  bars,  which  support 
the  weight. 


THE    HYDRAULIC    JACK 

This  is  a  lifting  apparatus  operated  by  means  of  a  liquid  acting 
against  a  piston  to  raise  it,  the  pressure  on  the  liquid  being  produced 
by  a  force  pump.  There  are  two  kinds  of  Dudgeon's  hydraulic  jacks, 
the  base  and  the  horizontal,  the  principle  and  method  of  operation 
being  the  same  in  both.  There  are  also  three  sizes  supplied  by  the 
Ordnance  Department  capable  of  lifting  15,  20  and  30  tons  respect- 
ively. Both  larger  and  smaller  jacks  than  these  are  also  manufactured, 
and  can  be  obtained  where  needed. 

A  sectional  view  of  the  horizontal  jack  is  shown  in  Fig.  74,  with  the 
names  of  the  different  parts. 

Instructions  for  using. — Fill  the  jack,  when  the  ram  is  quite  down, 
through  the  screw-hole  in  the  head,  within  half  an  inch  from  the  top, 
with  alcohol  1  part,  water  2  parts  and  add  a  tablespoonful  of  sperm  oil. 

Never  fill  with  water,  kerosene  or  wood  alcohol.  Water  is  dangerous 
on  account  of  its  liability  to  freeze  and  to  rust  the  jack  when  not  in  use. 
Kerosene  destroys  the  packings,  and  wood  alcohol  corrodes  the  metal 
surfaces  and  destroys  the  packings. 

Heavy  oils  and  glycerin  soften  the  packings  and  gum  clog  the  valve 
ports. 

The  screw  in  the  head  is  not  intended  to  fit  tightly,  as  an  air  passage 
is  cut  in  it. 

Be  careful  that  no  dirt  gets  into  the  reservoir  in  filling. 

Occasionally  clean  it  out  and  refill  it,  as  the  liquid  becomes  thick  and 
the  jack  will  not  then  work  well. 

Always  keep  the  ram  quite  down  when  not  in  use. 

In  using,  place  the  head  or  the  claw  under  the  weight  to  be  raised. 
Put  in  the  lever  with  the  projection  downward.  Work  it  until  the 
weight  is  at  the  required  height,  or  the  number  of  inches  the  jack  runs 
out.  Sometimes  it  happens  that  another  stroke  of  the  lever  will  raise 
the  weight  too  high;  then  raise  the  lever  and  push  it  down  slowly, 
by  which  a  stroke  will  be  missed. 


480 


THE   SERVICE   OF   COAST  ARTILLERY 


In  most  jacks  there  is  a  tell-tale  hole  in  the  cylinder  which  lets  the 
liquid  out  when  the  ram  is  raised  beyond  the  safety  point. 

To  lower  the  weight  with  the  old-style  jacks,  push  the  lever  to  the 
bottom  of  the  stroke,  take  it  out,  and  insert  it  with  the  projection 
upward  and  with  a  slight  pressure  of  the  hand  the  weight  will  be 


PUMP  - 


RAM 


6CHE7WT/C  -SECTION 

V/ILVES 


SECTION  •  A77V  • 


A.  Ram. 

B.  Cylinder. 

C.  Reservoir. 

D.  Piston  cap. 

E.  Knuckle. 

F.  Pump  piston. 
H.  Piston  lever. 

b.  Ram  packing  ring. 


c.  Ram  packing  ring  nut. 

d.  Ram  packing. 

/.  Pump  small  nut. 
g.  By-pass  channel. 
h.  Pump-valve  bonnet. 
j.  Pump-valve  spring. 
k.  Nut. 
I.  Packing. 

FIG.  74. 


n.  Pump  nut. 

p.  Piston  valve  bonnet. 

r.  Piston  valve, 

s.  Piston  packing. 

t.  Piston  packing  ring. 

w.  Screw-valve  tripping  rod. 

x.  Pump  valve. 


lowered  as  slowly  as  required,  or  stopped  at  any  point.  Do  not  push 
the  lever  down  quickly,  but  slowly,  tapping  it  a  little  with  the  hand. 

If  the  valve  should  stick  on  its  seat  (in  which  case  the  jack  will 
not  work),  strike  the  lever  a  few  sharp  blows  up  and  down,  jarring  the 
valve  and  removing  the  difficulty. 

With  the  latest  improved  jacks,  that  have  the  screw  valve  w;  to 
raise  the  weight,  screw  this  valve  down  tight  on  its  seat  with  the  wheel 


CORDAGE  481 

before  beginning  to  pump.  To  lower,  unscrew  the  same ;  two  full  turns 
are  sufficient  to  lower  as  fast  as  required. ,  It  can  be  lowered  fast  or 
slowly  by  unscrewing  the  valve  from  its  seat  any  distance  up  to  two 
turns,  and  can  be  checked  by  screwing  the  valve  back  to  its  seat. 

These  jacks  may  be  used  equally  well  in  horizontal  or  upright 
positions  except  that  care  must  be  exercised  not  to  leave  them  too 
long  in  a  horizontal  position,  as  there  is  then  a  leakage  of  the  liquid 
through  the  vent,  and  the  pump,  F,  must  always  be  submerged  in 
order  that  it  may  work. 

A  jack  not  in  use  should  be  kept  filled  and  pumped  up  under  pressure 
at  least  once  a  month. 


TO    REPAIR   JACKS 

Instructions  for  Repairing  Jacks. — Trouble  with  hydraulic  jacks 
is  most  frequently  caused  by  rust  or  by  foreign  substances  within  the 
jack  and  good  care  is  essential  to  keep  a  jack  in  order.  Without  this,  it 
is  useless  to  expect  it  to  give  satisfaction.  Rust  and  sand  or  grit  will 
soon  injure  the  valves,  packings,  and  polished  surfaces  of  the  cylinder 
and  pump,  and  these  are  the  vulnerable  parts  of  all  hydraulic  appliances. 

The  packing  and  the  valves  are  very  simple,  and  the  following 
directions  will  give  all  the  information  necessary  to  keep  them  in  order: 

If  the  filling  flows  over  the  top  of  the  cylinder  or  through  the  cylinder 
vent,  the  ram  packing  leaks.  Remove  the  ram  from  the  cylinder,  and 
if  the  packing  is  only  worn,  place  a  strip  of  very  thin  tin  under  it.  If  it  is 
broken  or  torn,  unscrew  the  packing  rings,  put  on  a  new  papking,  and 
replace  the  rings.  If  the  packing  is  too  large,  or  if  the  ram  does  not  run 
down  easily,  take  off  a  very  little  from  the  outside  of  the  packing  with 
a  clean  file  or  rasp.  Be  careful  not  to  take  off  too  much,  for  a  new 
packing  must  be  reasonably  tight,  as  it  will  soon  wear  smooth.  Fit 
a  new  packing  tight  enough  to  require  the  weight  of  two  men  to  force 
down  the  ram,  for  if  the  packing  is  made  too  slack,  it  will  soon  leak.  The 
bottom  packing  seldom  gives  trouble,  and  should  last  for  years.  If, 
however,  it  becomes  necessary  to  renew  it,  it  should  be  done  by  driving 
it  from  the  upper  end  of  the  cylinder  to  the  bottom. 

If  the  piston  packing  becomes  worn,  unscrew  the  head,  draw  out 
the  piston,  renew  the  packings,  and  file  off  the  edges  to  fit  the  pump. 

To  remove  the  piston  of  the  horizontal  jack,  unscrew  the  cap;  turn 
back  the  socket  until  the  arm  is  disengaged,  and  draw  out  the  piston. 

If  the  valves  or  valve  seats  become  worn  or  scratched,  unscrew  the 


482  THE  SERVICE  OF  COAST  ARTILLERY 

valve  bonnets  and  regrind  the  valves  with  oil  and  very  fine  flour  of 
emery.  Be  careful  not  to  grind  the  valves  too  much,  and  to  wash  the 
valves  and  seat  perfectly  free  from  emery  before  replacing  the  valves. 

The  piston  valve  of  the  horizontal  jack  is  reached  by  removing 
the  piston,  as  before  described,  and  the  pump  valve  by  unscrewing 
the  pump-valve  bonnet  in  the  bottom  of  the  cistern. 

If  the  ram  does  not  rise  when  pumping,  examine  the  piston  valve; 
if  the  lever  rises  when  the  hand  is  removed,  examine  the  pump  valve. 


CHAPTER    XII 
MAGAZINE    RIFLE 

THE  U.  S.  magazine  rifle,  model  of  1903,  caliber  .30,  is  shown  in 
Fig.  75.  It  is  equipped  with  a  rear  sight,  model  of  1905,  a  knife  bayonet, 
model  of  1905,  and  gun  sling,  model  of  1907.  The  appendages  of  the 
rifle  consist  of  front  sight  cover;  the  oiler  and  thong  case  (carried  in 
•the  butt  of  the  stock),  consisting  of  an  oiler  and  dropper,  thong  and 
brush  complete.  The  accessories  of  the  rifle  consist  of  a  brass  cleaning 
rod  and  screw  driver.  A  kit  of  tools  is  issued  to  each  company  or 
troop  and  to  each  regimental  or  post  ordnance  officer  for  use  in  repair- 
ing the  rifle  and  bayonet. 

The  rifle  proper  consists  of  89  component  parts.  The  bayonet 
proper  consists  of  12  component  parts. 

The  total  weight  of  the  arm,  including  bayonet,  oiler  and  thong 
case,  is  9.69  pounds.  The  bayonet  weighs  1  pound. 

The  total  length  of  the  gun,  without  bayonet,  is  43.212  inches. 
The  total  length  of  bayonet,  is  20.56  inches.  The  total  length  of  gun 
and  bayonet  (when  attached)  is  58.96  inches. 

The  caliber  is  .30  of  an  inch.  The  rifling  consists  of  four  plain 
grooves,  0.004  inch  deep;  the  grooves  are  three  times  the  width  of  the 
lands.  The  ^wist  of  rifling  is  uniform,  one  turn  in  10  inches. 

The  rifle  is  stamped  with  the  Ordnance  escutcheon,  together  with 
the  initials  of  the  place  of  manufacture  and  the  month  and  year;  this 
stamp  is  on  the  top  in  rear  of  the  front  sight  stud.  Those  manufactured 
prior  to  1906  are  stamped  with  the  year  but  without  the  month. 

The  magazine  holds  five  cartridges.  The  trigger  pull  is  equal  to 
from  3  to  4^  pounds,  measured  at  middle  point  of  bow  of  the  trigger. 

The  computed  maximum  range  is  5,465  yards,  with  a  time  of  flight 
of  31.36  seconds.  Elevation  45  degrees.  Initial  velocity,  2,700  feet 
per  second.  Powder  pressure  in  chamber,  about  49,000  pounds  per 
square  inch. 

483 


484 


THE   SERVICE   OF   COAST  ARTILLERY 


I 


e 


POINTS   IN   HANDLING 

If  it  is  desired  to  carry  the  piece  cocked,  with  a  cartridge  in  the 
chamber,  the  bolt  mechanism  should  be  secured  by  turning  the  safety 

lock  fully  to  the  right.  If  this  is  not  done 
the  rifle  may  be  discharged  upon  turning 
the  safety  lock  fully  to  the  ready  position. 

Under  no  circumstances  should  the  firing 
pin  be  let  down  by  hand  on  a  cartridge  in 
the  chamber. 

To  obtain  positive  ejection,  and  to  in- 
sure the  bolt  catching  the  top  cartridge  in 
magazine,  when  loading  from  the  magazine, 
the  bolt  must  be  drawn  fully  to  the  rear 
in  opening  it. 

The  piece  is  habitually  carried  locked; 
that  is,  with  the  safety  lock  at  the  "safe." 
It  is  always  locked  after  executing  cease 
firing. 

To  prevent  accidents,  the  chamber  is 
opened  and  the  magazine  examined  when 
troops  are  first  formed  and  again  just  be- 
fore they  are  dismissed.  When  rifles  are 
not  in  use,  as,  for  instance,  when  they  are 
in  gun  racks,  etc.,  the  trigger  should  be 
pulled  to  relieve  the  strain  on  the  spring. 

The  cut  off  is  kept  turned  "off "except 
when  actually  using  cartridges. 

When  the  bolt  is  closed,  or  slightly  for- 
ward, the  cut  o/f  may  be  turned  up  or  down, 
as  desired.  When  the  bolt  is  in  its  rear- 
most position,  to  pass  from  loading  from 
the  magazine  to  single  loading,  it  is  neces- 
sary to  force  the  top  cartridge  or  follower 
below  the  reach  of  the  bolt,  to  push  the 
bolt  slightly  forward  and  to  turn  the  cut 
off  down,  showing  "off." 

In  aiming  the  rifle,  care  should  be  exer- 
cised that  the  fingers  do  not  cover  the  gas 
escape  hole  just  above  and  to  the  rear  of  the  grasping  groove  on  the 
right  side  of  the  piece. 


MAGAZINE   RIFLE  485 

In  case  of  a  misfire  it  is  unsafe  to  draw  back  the  bolt  immediately, 
as  it  may  be  a  case  of  hang  fire.  In  such  cases  the  piece  should  be 
cocked  by  drawing  back  the  cocking  piece. 

The  bayonet  is  not  fixed  except  for  instruction,  in  bayonet  exercise, 
on  guard,  or  when  needed  for  purposes  of  defense  or  offense. 

Experimental  firing  and  laboratory  experiments  show  that,  all 
other  conditions  being  identical,  the  muzzle  velocity  of  ammunition 
loaded  with  smokeless  powder  will  be  increased  by  exposure  to  a  higher 
atmospheric  temperature,  and  decreased  by  a  lower. 

Variations  in  the  barometric  pressure  and  the  percentage  of  humidity 
of  the  air  will  also  cause  variations  in  the  velocity;  consequently  the 
elevation  for  any  range  will  vary  slightly  with  these  conditions.  More- 
over, the  velocity  of  78  feet  stamped  upon  the  bandoleers  may  vary, 
in  different  issues  of  ammunition,  20  feet  on  either  side  of  the  standards. 
The  muzzle  velocity  obtained  in  different  rifles  also  varies  with  the  same 
ammunition. 

In  adjusting  the  sight  for  elevation  at  any  range,  it  must  be  borne 
in  mind  that  in  addition  to  the  allowance  made  for  variations  in  the 
velocity  of  the  ammunition,  allowance  must  also  be  made  for  the  effect 
of  differences  in  light,  the  amount  of  front  sight  seen,  the  effect  of 
mirage  on  the  target,  the  effect  of  heat  developed  in  the  gun  in  firing, 
the  condition  of  the  bore  as  to  cleanliness,  the  personal  equation  of  the 
firer,  the  peculiarities  of  individual  guns,  etc. 

The  graduations  of  the  rear  sight  are  correct  only  for  the  particular 
conditions  existing  when  they  were  experimentally  determined,  con- 
sequently, in  adjusting  the  sight  for  elevation  at  any  range,  allowance 
must  be  made  for  whatever  change  in  the  elevation  the  difference 
between  the  former  and  the  present  conditions  produces. 


DISMOUNTING   AND   ASSEMBLING 

Figure  76  shows  the  bolt  and  magazine  mechanism.  They  can  be  dis- 
mounted without  removing  the  stock.  The  latter  should  never  be 
done,  except  for  making  repairs,  and  then  only  by  some  selected  and 
instructed  man. 

To  Dismount  the  Bolt  Mechanism,  place  the  cut  off  at  the  center 
notch;  cock  the  arm  and  turn  the  safety  lock  to  a  vertical  position; 
grasp  the  piece  as  shown  in  Fig.  77,  raise  the  bolt  handle  and  draw 
out  the  bolt. 

Hold  the  bolt  in  the  left  hand  as  shown  in  Fig.  78,  press  sleeve  lock 


486 


THE   SERVICE   OF   COAST  ARTILLERY 


in  with  the  thumb  of  right  hand  to  unlock  sleeve  from  bolt  and  unscrew 
sleeve  by  turning  to  the  left. 

Hold  the  sleeve  between  the  forefinger  and  thumb  of  the  left  hand, 
draw  cocking  piece  back  with  the  middle  finger  and  thumb  of  the  right 


Cl/T Off Sf/MOif 


CUTOFF      &CCTORPIN 


xirc>v./-mtfr        STOCK 


FIG.  76. 

hand,  turn  safety  lock  down  to  the  left  with  the  forefinger  of  the  right 
hand,  in  order  to  allow  the  cocking  piece  to  move  forward  in  sleeve, 
thus  partially  relieving  the  tension  of  mainspring;  with  the  cocking 
piece  against  the  body,  draw  back  the  firing-pin  sleeve  with  the  fore- 


FIG.  77. 


finger  and  thumb  of  the  right  hand  and  hold  it  in  the  position  shown  in 
Fig.  79,  while  removing  the  striker  with  the  left  hand;  remove  firing- 
pin  sleeve  and  mainspring;  pull  firing  pin  out  of  sleeve;  turn  the 
extractor  to  the  right,  forcing  its  tongue  out  of  its  groove  in  the  front 


MAGAZINE  RIFLE 


487 


of  the  bolt,  and  force  the  extractor  forward  as  shown  in  Fig.  80,  until 
it  is  off  the  bolt. 

To  Assemble  Bolt  Mechanism,  with  the  left  hand  grasp  the  rear  of 
the  bolt,  handle  up;   with  the  thumb  and  forefinger  of  the  right  hand 


FIG.  78. 

turn  the  extractor  collar  until  its  lug  is  on  a  line  with  the  safety  lug- 
on  the  bolt;  take  the  extractor  in  the  right  hand  and  insert  the  lug  on 
the  collar  in  the  undercuts  in  the  extractor  by  pushing  the  extractor  to 
the  rear  until  its  tongue  comes  in  contact  with  the  rim  on  the  face  of 


COCKING  PIECE. 
\ 


FIG.  79. 


the  bolt  (a  slight  pressure  with  the  left  thumb  on  the  top  of  the  rear 
part  of  the  extractor  assists  in  this  operation);  turn  the  extractor  to 
the  right  until  it  is  over  the  right  lug;  take  the  bolt  in  the  right  hand 


488 


THE   SERVICE   OF  COAST  ARTILLERY 


and  press  the  hook  of  the  extractor  (Fig.  81)  against  the  butt  plate  or 
some  rigid  object,  until  the  tongue  on  the  extractor  enters  its  groove 
in  the  bolt. 

With  the  safety  lock  turned  down  to  the  left  to  permit  the  firing 
pin  to  enter  the  sleeve  as  far  as  possible,  assemble  the  sleeve  and  firing 


FIG.  80. 

pin;  place  the  cocking  piece  against  the  body  and  put  on  mainspring, 
firing-pin  sleeve,  and  striker  (Fig.  79) ;  hold  the  cocking  piece  between 
the  thumb  and  forefinger  of  the  left  hand,  and  by  pressing  the  striker 
point  against  some  substance,  not  hard  enough  to  injure  it,  force  the 
cocking  piece  back  until  the  safety  lock  can  be  turned  to  the  vertical 
position  with  the  right  hand ;  insert  the  firing  pin  in  the  bolt  and  screw 


GROOVE.- 


IXTBACTOR  COLLAE.         SAFETY  LOO. 


FIG.  81. 

up  the  sleeve  (by  turning  it  to  the  right)  until  the  sleeve  lock  enters  its 
notch  on  the  bolt. 

See  that  the  cut  off  is  at  the  center  notch;  hold  the  piece  under  the 
floor  plate  with  the  fingers  of  the  left  hand,  the  thumb  extending  over  the 
left  side  of  the  receiver;  take  bolt  in  right  hand  with  safety  lock  in 
a  vertical  position  and  safety  lug  up;  press  rear  end  of  follower  down 
with  the  left  thumb  and  push  bolt  into  the  receiver;  lower  bolt 
handle;  turn  safety  lock  and  cut  off  down  to  the  left  with  right  hand. 

To  Dismount  Magazine  Mechanism,  with  the  bullet  end  of  a  cartridge 
press  on  the  floor  plate  catch  (through  the  hole  in  the  floor  plate),  at 


MAGAZINE  RIFLE  489 

the  same  time  drawing  the  bullet  to  the  rear;  this  releases  the  floor 
plate. 

Raise  the  rear  end  of  the  first  limb  of  the  magazine  spring  high 
enough  to  clear  the  lug  on  the  floor  plate  and  draw  it  out  of  its  mortise ; 
proceed  in  the  same  manner  to  remove  the  follower. 

To  assemble  magazine  spring  and  follower  to  floor  plate,  reverse 
operation  of  dismounting. 

Insert  the  follower  and  magazine  spring  in  the  magazine,  place  the 
tenon  on  the  front  end  of  the  floor  plate  in  its  recess  in  the  magazine, 
then  place  the  lug  on  the  rear  end  of  the  floor  plate  in  its  slot  in  the 
guard,  and  press  the  rear  end  of  the  floor  plate  forward  and  inward  at  the 
same  time,  forcing  the  floor  plate  into  its  seat  in  the  guard. 


CLEANING   AND   CARE 

As  the  bore  of  the  rifle  is  manufactured  with  great  care  in  order 
that  a  high  degree  of  accuracy  may  be  obtained,  it  should  be  attentively 
cared  for.  The  residuum  from  smokeless  powder  tends  to  corrode  the 
bore  and  should  therefore  be  removed  as  soon  after  firing  as  practicable. 
The  following  method  has  been  practiced  with  good  results :  Using  the 
cleaning  rod  and  small  patches  of  cloth  (preferably  canton  flannel), 
clean  the  bore  thoroughly  with  the  patches  soaked  in  a  saturated 
solution  of  soda  and  water.  Then  thoroughly  dry  the  bore  and  remove 
the  soda  solution  by  the  use  of  dry  patches,  and  finally  oil  the  bore  with 
patches  soaked  in  cosmic  oil.  Twenty-four  hours  after  this  first  clean- 
ing, the  bore  should  be  again  cleaned  as  described  above,  as  it  has  been 
found  that  the  powder  gases  are  probably  forced  into  the  texture  of 
the  steel  and  will,  if  the  second  cleaning  is  not  resorted  to,  cause  rusting 
no  matter  how  thoroughly  the  bore  may  have  been  cleaned  at  first. 
If,  however,  a  cleaning  rod  is  not  at  hand,  the  barrel  should  be  cleaned 
as  thoroughly  as  possible  by  means  of  the  thong  brush  and  rags,  and 
oiled  as  explained  above. 

To  clean  or  oil  the  bore  with  rags,  the  thong  brush  is  unscrewed, 
the  rag  placed  in  the  rag  slot  of  the  thong  tip  and  drawn  from  the 
muzzle  toward  the  breech. 

As  neither  the  ramrod  nor  jointed  cleaning  rod  is  issued  with  this 
rifle,  the  brass  cleaning  rod  should  be  carried  into  the  field  whenever 
practicable. 

If  gas  escapes  at  the  base  of  the  cartridge,  it  will  probably  enter 
the  well  of  the  bolt  through  the  striker  hole.  In  this  case  the  bolt 


490  THE   SERVICE   OF  COAST  ARTILLERY 

mechanism  must  be  dismounted  and  the  parts  and  well  of  the  bolt 
thoroughly  cleaned. 

Before  assembling  the  bolt  mechanism,  the  firing  pin,  the  barrel 
of  the  sleeve,  the  body  of  the  striker,  the  well  of  bolt,  and  all  cams  should 
be  lightly  oiled. 

Many  of  the  parts  can  generally  be  cleaned  with  dry  rags.  All  parts 
after  cleaning  should  be  wiped  with  an  oiled  rag. 

The  best  method  of  applying  oil  is  to  rub  with  a  piece  of  cotton 
cloth  upon  which  a  few  drops  of  oil  have  been  placed,  thereby  avoiding 
the  use  of  an  unnecessary  amount  of  oil.  This  method  will,  even  in 
the  absence  of  the  oiler,  serve  for  the  cams  and  bearings,  which  should 
be  kept  continually  oiled. 

Any  part  that  may  appear  to  move  hard  can  generally  be  freed  by 
the  use  of  a  little  oil.  Sperm  oil  only  should  be  used  for  lubricating 
metallic  bearing  and  contact  surfaces. 

For  the  chamber  and  bore,  only  cosmoline  or  cosmic  should  be  used. 
This  should  also  be  applied  to  all  metallic  surfaces,  to  prevent  rusting 
when  arms  are  stored  or  when  not  used  for  an  appreciable  length  of 
time. 

The  stock  and  hand  guard  may  be  coated  with  raw  linseed  oil  and 
polished  by  rubbing  with  the  hand. 


GUN   SLING 

The  gun  sling,  model  of  1907,  is  made  of  four  parts,  the  long  strap, 
the  short  strap  and  two  keepers.  To  assemble  it,  the  plain  end  of  the 
long  strap  is  passed  through  the  larger  keeper,  then  through  the  metal 
loop  of  the  short  strap,  passing  from  the  undressed  to  the  dressed  side 
of  the  latter,  then  back  through  the  larger  keeper,  forming  the  arm  loop, 
•dressed  side  out.  The  same  end  is  then  passed  through  the  smaller 
keeper,  through  the  lower  band-sling  swivel — called  the  upper  sling 
swivel,  from  the  butt  toward  the  muzzle,  and  back  through  the  smaller 
keeper,  the  arm  loop  being  completed  by  engaging  the  claw  of  the  long 
strap  in  the  proper  holes  in  the  other  end  of  same.  The  size  of  the 
arm  loop  is  adjusted  to  suit  the  individual  who  is  to  fire  the  piece,  the 
loop  being  drawn  through  the  upper  swivel  until  the  claw  comes  well  up 
toward  the  upper  swivel.  The  claw  end  of  the  short  strap  is  then  passed 
through  the  lower  swivel  from  muzzle  to  butt  and  brought  up  and 
engaged  in  the  proper  holes  in  the  long  strap,  drawing  the  sling  taut. 
This  gives  the  parade  position  of  the  sling.  To  adjust  it  for  firing  or 


MAGAZINE  RIFLE  491 

carrying,  the  claw  of  the  short  strap  is  disengaged  and  re-engaged  in 
the  proper  holes  of  the  short  strap,  no  change  being  necessary  in  the 
adjustment  of  the  arm  loop. 


AMMUNITION 

Ammunition  for  this  arm  is  assembled  in  clips  to  facilitate  load- 
ing. Ammunition  issued  is  as  follows: 

The  Caliber  .30  Ball  Cartridge  is  shown  in  Fig.  82.  It  consists  of  a 
case,  primer,  charge  of  smokeless  powder,  and  bullet.  The  case  is  of 
cartridge  brass.  It  has  a  conical  body  joined  by  a  sharper  cone,  called 
the  shoulder,  to  the  neck,  which  is  the  seat  of  the  bullet  and  very  nearly 
cylindrical.  The  front  end  of  the  case  is  called  the  mouth  and  the  rear 


FIG.  82. 

end  the  head.  The  latter  is  grooved  to  provide  for  extraction  of  the 
cartridge  from  the  chamber  of  the  rifle,  and  is  provided  with  a  primer 
pocket  and  vent.  The  initials  of  the  place  of  manufacture,  the  number 
of  the  month,  and  the  year  of  its  fabrication  are  stamped  on  the  head 
of  the  case. 

The  primer  consists  of  the  cup,  percussion  composition,  disc  of 
shellaced  paper,  and  anvil.  The  cup  is  of  gilding  metal  and  contains 
.48  grain  of  non-fulminate  composition  composed  of  tersulphide  of 
antimony,  potassium  chlorate,  sulphur  and  ground  glass.  A  disc  of 
shellaced  paper  covers  the  composition  to  protect  it  from  moisture  and 
to  prevent  electrolytic  action.  The  anvil  is  of  brass  and  is  assembled 
over  the  paper.  After  the  primer  is  assembled  to  the  case  a  drop  of 
shellac  is  placed  on  the  head  of  the  primer  to  make  the  joint  waterproof. 

The  charge  is  of  pyrocellulose  composition  very  similar  to  the 
powders  used  as  propelling  charges  in  seacoast  guns.  The  grains  are 
cylindrical,  single,  perforated  and  graphited.  The  normal  charge 
weighs  from  48  to  50  grains,  varying  with  the  lot  of  powder  used. 

The  bullet  has  a  core  of  lead  and  tin  composition  inclosed  in  a 
jacket  of  cupro  nickel.  It  weighs  150  grains,  and  the  point  is  much 


492 


THE   SERVICE   OF  COAST  ARTILLERY 


sharper  and  offers  less  resistance  to  the  air  than  that  of  any  previous 
model.  The  sides  of  the  bullet  are  smooth  and  its  base  flat.  The 
portion  inclosed  in  the  neck  of  the  case  is  covered  with  a  lubricant  of 
japan,  wax  and  graphite.  A  pressure  of  at  least  75  pounds  is  required 
to  seat  the  bullet  in  the  case,  resulting  in  the  case  being  waterproof. 

The  standard  muzzle  velocity  of  this  ammunition  in  the  rifle  is 
2,700  feet  per  second.  The  instrumental  velocity  measured  at  78  feet 
from  the  muzzle  is  2,640  feet  per  second,  with  an  allowed  mean  varia- 
tion of  20  feet  per  second  on  either  side  of  the  standard.  The  cartridge 
complete  weighs  392  grains,  its  weight  varying  slightly  with  variation 
in  the  weight  of  the  powder  charge.  Five  cartridges  are  packed  in  a 
clip,  a  drawing  of  which  is  shown  in  Fig.  83.  The  clip  for  dummy 


FIG.  83. 

cartridges  has  square  instead  of  round  ends  and  the  tongues  on  the 
spring  are  omitted. 

Sixty  ball  cartridges  in  twelve  clips  are  packed  in  a  bandoleer  which 
is  made  of  olive  drab  cloth  and  contains  six  pockets,  each  holding  two 
clips.  It  weighs,  with  cartridges,  3.88  pounds.  Each  bandoleer  is 
stamped  with  the  number  and  kind  of  cartridges  it  contains,  the  place 
of  manufacture,  the  instrumental  velocity  and  the  date  of  loading. 


FIG.  84. 

The  Blank  Cartridge  is  shown  in  Fig.  84.  It  differs  from  the  ball 
cartridge  in  the  charge  of  powder,  in  the  bullet,  and  in  the  fact  that  the 
case  is  tinned.  The  bullet  is  of  paper,  hollow,  and  contains  a  charge  of 


MAGAZINE   RIFLE 


493 


5  grains  of  "E.G."  smokeless  powder,  which  insures  the  breaking  up 
of  the  bullet  on  leaving  the  bore.  This  charge  is  retained  in  the  bullet 
by  a  drop  of  shellac.  A  coating  of  paraffin  on  the  outside  of  the  bullet 
prevents  the  absorption  of  moisture  by  the  paper.  The  propelling 
charge  is  10  grains  of  "E.G."  powder.  The  cartridge  is  made  0.1  inch 
shorter  than  the  ball  cartridge.  This  is  a  measure  of  protection  against 
the  accidental  assembling  by  the  machine  of  a  ball  cartridge  in  a  clip 
of  blank  ones. 

The  Dummy  Cartridge  is  shown  in  Fig.  85.     It  is  tinned  and  pro- 
vided with  six  longitudinal  corrugations,  also  three  circular  holes  in  the 


FIG.  85. 

corrugated  portion.  The  tinning,  corrugations,  and  holes  afford 
unmistakable  means  for  distinguishing  the  dummy  from  the  ball 
cartridge,  both  by  sight  and  touch.  The  bullet  is  the  same  as  in  the 
ball  cartridge.  The  dummy  primer  has  cup  and  anvil,  but  no  percussion 
composition. 

The  Guard  Cartridge  is  shown  in  Fig.  86.     It  differs  from  the  ball 
cartridge  in  the  charge  of  powder  and  in  the  fact  that  second-class 


r 


FIG.  86. 

bullets  having  slight  imperfections  are  used.  Five  cannelures  encircle 
the  body  of  the  case  at  about  the  middle,  affording  means  for  distinguish- 
ing it  from  the  ball  cartridge  by  either  sight  or  touch. 

The  charge  consists  of  about  9.1  grains  bullseye  powder;  or  16.7 
grains  DuPont  Rifle  Smokeless  No.  1,  giving  a  muzzle  velocity  of  1,200 
feet  per  second.  This  cartridge  gives  good  results  at  100  yards  and  has 
sufficient  accuracy  for  use  at  150  and  200  yards.  The  range  of  100 
yards  requires  a  sight  elevation  of  450  yards,  and  ranges  of  200  and  300 
yards  require  elevations  of  650  and  850  yards,  respectively. 


CHAPTER  XIII 
POINTS  FOR  COAST  ARTILLERISTS 

IT  is  the  object  of  these  points  to  facilitate  the  study  of  the  Drill 
Regulations.  They  are  given  merely  as  suggestions  of  methods  for 
obtaining  practical  results  as  well  as  uniformity  of  commands  during 
drill  or  action. 

BATTLE    COMMANDERS 

• 

The  general  principles  governing  battle-command  combat  involve 
the  best  means  to  pursue  in  order  to  destroy  the  enemy  with  the  greatest 
dispatch  and  the  least  confusion  on  the  one  hand,  and  economy  of 
ammunition  and  the  preservation  of  the  life  of  the  guns  by  the  preven- 
tion of  useless  fire,  on  the  other. 

No  attempt  should  be  made  to  develop  a  regular  routine  of  drill. 
Each  battle  commander  should  conduct  his  drills  according  to  the 
development  of  the  particular  problem  in  hand,  and  rules  as  to  the 
procedure  of  particular  batteries  or  fire  commands  should  be  applied 
with  reference  to  the  development  of  this  problem. 

"General  defense  plans"  authorized  for  use  as  suitable  commands 
during  battle-command  drill  or  action,  are  undoubtedly  effective,  since 
they  lead  to  a  proper  general  understanding  of  fire  control  as  it  is  to  be 
applied  under  normal  conditions  of  combat.  They  unquestionably 
tend  to  perfect  organization  among  the  several  tactical  units,  but  they 
are  not  intended  to  be  accepted  as  the  only  means  through  which  a 
battle  command  may  be  fought,  as  they  are  necessarily  theoretical  in 
that  their  practical  utility  has  never  been  demonstrated  in  action. 

It  should  be  borne  in  mind  that  the  " normal' '  time  for  an  attack 
from  the  sea  would  be  at  night  or  in  rainy  or  misty  weather  when  great 
difficulty  is  to  be  anticipated  in  locating  particular  ships  of  a  column  or 
line,  as,  for  instance,  "the  first  and  last  battle  ship  of  a  column"  or 
"the  ships  in  order  in  line  from  right  to  left." 

Battle  commanders  should  study  to  maintain  control  of  their 
commands  even  after  they  have  passed  the  several  subdivisions  into 

494 


POINTS  FOR  COAST  ARTILLERISTS  495 

the  hands  of  fire  or  battery  commanders.  Experience  with  one  of  the 
most  important  battle  commands  on  the  Atlantic  seaboard  under 
assimiliated  service  conditions  indicates  that  the  ideal  battle  command 
drill  is  that  in  which  the  several  subdivisions  are  not  committed  to  any 
general  line  of  action  but  are  retained  under  the  personal  control  of 
the  battle  commander  until  the  action  has  developed  to  a  point  where 
the  battle  commander  may  safely  eliminate  certain  targets  or  ships 
from  the  general  action  by  their  assignment  to  particular  batteries  or 
units. 

Should  the  topographical  or  marine  features  of  a  harbor  prevent 
the  assailants  from  attacking  in  any  formation  but  that  of  column, 
the  concentration  of  fire  on  the  leading  ship  by  say  75  per  cent,  of  the 
primary  armament  (keeping  the  others  in  reserve)  by  the  command, 
"  Fire  at  ships  in  order  in  column/'  meaning,  as  it  does,  that  the  fire  is 
to  be  concentrated  on  the  leading  ship  until  it  is  out  of  action  and  then 
changed  to  the  next  and  so  on,  would  seem  to  be  logical,  thoroughly 
simple  and  practical.  The  moral  effect  of  the  quick  destruction  of 
the  leading  ship  would  be  severe  on  the  personnel  of  the  remaining  vessels 
and  inspiring  to  those  ashore.  Again,  the  destruction  of  the  first  ship 
would  place  her  directly  in  the  path  of  the  others  and  possibly  block 
their  further  approach. 

At  this  point  the  battle  commander's  action  would  be  guided  by  his 
newly  acquired  knowledge  of  the  destructiveness  of  his  armament.  There 
are  no  data  available  on  which  to  found  an  absolutely  sure  estimate 
as  to  the  number  of  guns  that  can  with  certainty  be  counted  on  to  injure 
the  fighting  efficiency  of  a  ship  or  sink  her.  Accordingly,  if  the  battle 
commander  found  at  this  stage  of  the  combat  that  two  batteries  would 
have  been  sufficient  to  destroy  the  ship  with  dispatch,  the  moment 
for  the  distribution  of  the  heretofore  concentrated  stream  of  fire  would 
be  at  hand,  and  the  second  or  decisive  stage  of  the  action  developed. 

Should  the  fleet  press  the  action,  the  fort  or  forts  should  remain  in 
action  under  the  direction  of  the  battle  commander  in  accordance  with 
the  principles  already  enunciated,  namely  that  he  should  keep  under 
his  personal  control  all  the  elements  of  his  command  until  the  action 
has  developed  to  the  stage  where  he  can  safely  assign  ships  or  sub- 
divisions of  the  fleet  to  fire  or  battery  commanders,  and  thus,  as  before 
explained,  eliminate  them  from  the  general  action. 

On  the  other  hand ,  should  the  military  features  of  the  harbor  permit 
the  approach  of  the  assailants  in  line  or  line  of  columns,  a  subdivision 
of  the  fleet  should  receive  concentrated  action  of  say  50  per  cent,  of  the 
primary  armament  in  the  outer  defense  zone.  The  destruction  of  any 


496  THE  SERVICE   OF  COAST  ARTILLERY 

of  the  ships  fired  upon  at  the  longer  ranges  would  have  the  same  encourag- 
ing result  on  the  defenders  and  a  demoralizing  effect  on  the  assailants. 
From  this  stage  the  action  would  follow  the  same  general  lines  as  are 
laid  down  above. 

In  order  that  the  battle  commander  may  accomplish  the  tactical 
changes  indicated,  it  is  essential  that  the  artillery  discipline  and  artillery 
drill  be,  through  continued  practice,  so  perfected  that  in  actual  com- 
bat the  excitement  will  not  disurb  the  system  of  command  nor  cause 
any  unit  to  be  carried  away  to  the  extent  that  it  would  commence 
independent  action  without  waiting  orders  from  the  battle  commander. 

To  attain  such  a  state  of  excellence  in  artillery  drill  it  is  most  impor- 
tant that  the  larger  elements  of  the  command,  that  is,  fire  and  battle 
commands,  be  not  only  frequently  but  habitually  drilled  and  exercised. 


BATTLE  COMMAND  DRILL 

Battle  commanders  are  liable  to  endeavor  to  work  their  commands 
too  fast  during  drill.  They  should  constantly  keep  the  fact  in  mind 
that  they  have  under  their  control  a  military  machine  of  vast  dimensions, 
and  in  order  that  it  may  run  smoothly  each  part  must  necessarily  work 
without  needless  pressure  and  in  perfect  unison.  Undue  haste  should 
be  studiously  avoided. 

Floods  of  orders  tend  to  clog  the  parts  rather  than  facilitate  their 
action.  Absolute  silence  in  all  stations  should  be  insisted  upon.  Smoking 
should  be  strictly  prohibited. 

For  practice  in  deliberation  as  well  as  brevity,  battle  commanders 
should  personally  dictate  to  their  recorders  all  orders  they  desire  to 
have  transmitted.  They  should  constantly  endeavor  to  word  their 
communications  with  such  brevity  of  language  as  to  make  their  tran- 
scription comparatively  easy. 

All  general  orders  to  fire  commanders  should  be  given  as  soon  after 
the  stations  are  opened  as  practicable. 

The  words  "right,"  "left,"  " in  front  of,"  or  "in back  of,"  should  not 
be  used  in  describing  targets,  etc.  The  words,  "north,"  "south," 
"east,"  and  "west,"  can  always  be  used  with  ease  and  by  their  use 
the  likelihood  of  error  is  greatly  reduced. 

Unless  there  is  some  special  reason  for  so  doing,  battle  commanders 
should  not  specify  the  kind  of  projectile  to  be  used,  as  this  is  a  proper 
function  of  the  battery  commanders. 

As  soon  as  reports  have  been  received,  such  as:  "  F.  C.  Two,  In  order," 


POINTS  FOR  COAST  ARTILLERISTS  497 

"F.  C.  Five,  In  order/'  etc.,  the  battle  commander  may  begin  the  drill 
by  designating  the  target  or  targets ;  or  if  at  night  by  directing  fire  and 
mine  commanders  to  search  certain  areas  with  their  searchlights  and 
report  any  suspicious  vessels  to  him,  using  his  own  searchlight  as  a 
roving  light. 

The  following  scheme  for  the  drill  of  a  battle  command  consisting 
of  four  gun  fire-commands,  one  mortar  fire-command  and  one  mine 
command  is  given  as  an  example  and  may  be  modified  in  accordance  with 
the  strength  of  armament.  It  calls  for  Fire  Commander's  Action  in 
one  Fire  Command ;  Restricted  Fire  in  one  Fire  Command ;  Unrestricted 
Fire  in  one  Fire  Command ;  Battery  Commander's  Action  in  one  Fire 
Command;  One  Fire  Command  in  Reserve,  and  Mine  Command  in 
Action. 

"F.  C.  One;    Target  in  Battle  Beam;    Fire  Commander's  Action." 

"F.  C.  Two;   Prepare  for  Action  as  Reserve." 

"F.  C.  Three;  Target  in  Number  Three  Beam;  Each  Battery 
Fire  Five  Shots  at  Two-Minute  Interval." 

"F.  C.  Four;  *  Fire  at  Target  in  Battle  Beam  when  it  arrives  in 
seventh  zone." 

"F.  C.  Five;  f  When  target  representing  protected  cruiser  is  identi- 
fied begin  Battery  Commander's  Action." 

"Mine   C.  Protect  Mine  Field." 

By  interchanging  the  above  commands  a  very  complete  battle 
command  drill  can  be  executed. 


FIRE   COMMANDERS 

The  general  principles  and  rules  enumerated  in  connection  with 
battle  commanders  are  applicable  in  every  way  to  the  drill  or  action  of 
fire  commands,  and  should  be  studied  with  a  view  to  their  application 
and  development. 

Fire  commanders  should  remember  that  at  forts  where  the  horizontal- 
base  system  is  generally  used  apparent  delay  is  frequently  caused  in 
identifying  targets  by  the  secondary  observer,  whose  position  at  the 
other  end  of  a  long  base  line  often  makes  it  much  more  difficult  for  him 
to  find  the  target  than  the  primary  observer  and  gun  pointer.  In  order 
to  overcome  this  delay,  at  forts  where  the  vertical-base  system  can  also 


*  F.C.  Four,  assumed  to  be  mortars. 

t  F.C.  Five,  assumed  to  be  10-inch  batteries. 


498  THE  SERVICE   OF  COAST  ARTILLERY 

be  used,  fire  commanders  can  facilitate  action  by  issuing  a  general 
order  directing  that  as  soon  as  the  primary  observer  has  found  the 
target,  report  be  sent  to  him  ("Dix,  Target"*)  and  the  vertical-base 
system  used  until  such  time  as  secondary  locates  the  target. 

The  establishment  of  uniformity  in  commands  during  fire-command 
drill  or  action  is  necessary,  as  it  simplifies  communications  and  instantly 
gives  subordinates  unmistakable  information  as  to  the  wishes  of  the 
fire  commander. 

The  following  commands,  covering  the  general  drill  of  fire  commands, 
are  authorized.  They  are  particularly  recommended  on  account  of  their 
studied  brevity  and  simplicity.  Fire  commanders  should  insist  that 
officers  and  men  charged  with  the  transmission  of  communications  use 
the  exact  words  of  the  text  during  all  drills  and  exercises. 

In  case  recorders  are  not  available  at  battery  primary  stations,  or 
battery  commander's  stations,  should  the  fire  commander  desire  that  a 
message  or  order  to  a  battery  commander  be  written  down  upon  its 
receipt,  he  should  first  send  the  following: 

"Dix  (or,  All  Batteries),  Prepare  to  write  message." 

When  suitable  preparation  has  been  made,  announcement  of  readi- 
ness should  be  made  to  the  F.  C.,  as  follows: 

"Dix,   Ready." 

As  soon  as  the  batteries  of  a  fire-command  are  in  order,  or  need 
repairs  that  cannot  be  made  immediately,  the  following  message  should 
be  sent  to  F.  C.  by  each: 

"Dix,  In  order,"  or  "Dix,  T.  I.  Bell  not  ringing,"  or  "Dix,  Tele- 
phone to  guns  out  of  order,"  etc.,  etc. 

In  case  report  of  difficulty  is  received  the  F.  C.  should  direct  the 
electrician  sergeant  detailed  to  his  command  to  make  such  repairs  as 
may  be  needed. 

The  next  order  in  sequence  would  be: 

"All  Batteries  (or,  Dix),  Target;  Steamer  coming  in,  one  funnel, 
white  band,  main  ship  channel,  west  of  Norton's  Point  Light." 

When  target  has  been  identified  it  should  be  followed  and  F.  C. 
notified  as  follows: 

"Dix,  Target." 

In  case  the  target  cannot  be  found  after  suitable  effort  F.  C.  is  notified 
as  follows: 

"Dix,  Describe." 

In  this  case  the  F.  C.  may  send  further  particulars  of  description. 

*  The  word  "  Dix  "  is  used  to  designate  the  name  of  a  battery. 


POINTS  FOR  COAST  ARTILLERISTS  499 

In  case  the  F.  C.  desires  a  battery  to  take  another  target,  the 
following  order  is  sent: 

"Dix,  Change  Target.  Target;  Tug,  towing  two  barges,  coming 
in,  range  about  10,000  yards." 

In  case  a  battery,  after  having  identified  a  target,  tracks  same  until 
it  is  out  of  range,  the  following  message  is  sent  to  F.  C. 

"Dix,  Target  out  of  range." 

To  indicate  that  a  vessel  is  no  longer  to  be  fired  upon,  or  is  assumed 
to  have  been  destroyed,  the  following  message  is  sent: 

"  Target  out  of  action." 

To  place  the  control  of  a  battery  in  the  hands  of  the  battery  com- 
mander, the  following  command  is  proper:  "  Dix  (or,  All  Batteries), 
Battery  Commander's  Action." 


RESTRICTED   FIRE 

To  restrict  the  fire  during  a  fire  command  drill  or  action,  the  follow- 
ing commands  are  proper: 

"Dix  (or,  All  Batteries),  Fire  one  shot:  Commence  Firing."  (This 
restricts  to  one  shot  from  one  gun.) 

"Dix  (or,  All  Batteries),  Fire  one  (or  more)  rounds;  Commence 
Firing."  (A  round  consists  of  one  shot  from  each  gun  of  a  battery.) 

"Dix  (or,  All  Batteries),  Fire  at  two-minute  interval;  Commence 
Firing."  (This  means  that  one  round  is  to  be  hred  every  two  minutes 
by  the  battery  or  batteries  designated,  until  "Cease  Firing"  is  given.) 

"Dix  (or,  All  Batteries),  Fire  five  shots,  at  two  (three,  etc.)  minute 
interval;  Commence  Firing." 

"Dix  (or,  All  Batteries),  Fire  five  rounds  when  in  range  (or  at  9,000 
yards)." 

"Dix  (or,  All  Batteries),  Fire  at  Salvo  Point  No.  1  (or  No.  2,  etc.). 
(This  requires  the  battery  commander  (or  all  battery  commanders)  to 
fire  a  round  at  each  target  or  vessel  of  a  fleet  as  they  pass  the  designated 
salvo  point. 

UNRESTRICTED   FIRE 

The  following  commands  for  unrestricted  fire  are  proper: 
" Dix  (or,  All  Batteries),  Fire  at  ships  in  order  in  column;  Commence 
Firing."     (This  requires  the  battery  commander — or  all  battery  com- 
manders— to  concentrate  fire  on  the  first  vessel  in  the  column  until  it 
is  out  of  action  and  then  to  change  to  the  second  vessel  and  so  on.) 


500  THE   SERVICE   OF  COAST  ARTILLERY 

"Dix  (or,  All  Batteries),  Fire  at  ships  in  order  in  line  from  right 
to  left;  Commence  Firing."  (This  requires  the  battery  commander 
— or  all  battery  commanders — to  concentrate  fire  on  the  vessel  on  the 
right  of  the  enemy's  line,  until  it  is  out  of  action  and  then  change  to 
the  next  and  so  on.) 

"Dix  (or,  All  Batteries),  Target  under  fire;  Commence  Firing." 
(This  requires  the  concentration  of  fire  on  a  target  or  vessel  already 
being  fired  upon  by  another  battery  or  batteries.) 

"Dix  (or,  All  Batteries),  Fire  at  target;  Commence  Firing." 

At  the  conclusion  of  all  series  of  shots  fired,  battery  commanders 
should  report  as  follows: 

"Dix,  Series  completed." 

In  restricted  fire,  in  case  "cease  firing"  is  given  before  the  number 
of  shots  specified  have  been  fired,  battery  commanders  after  stopping  the 
fire  should  report: 

"Dix  (so  many)  shots  fired." 

In  case  the  command,  "Commence  Firing,  "is  again  given,  battery 
commanders  should  proceed  to  complete  the  series. 

For  the  purpose  of  finding  the  comparative  accuracy  of  ranges,  fire 
commanders  may  send  the  following  order: 

"All  batteries:  Send  range  of  target  to  F.  C.  at  next  bell." 

In  case  a  party  of  the  enemy  is  discovered  to  have  gained  access  to 
a  fort  unobserved,  and  provided  the  artillery  personnel  are  not  actually 
engaged  in  action  or  the  chances  of  artillery  action  are  remote,  fire 
commanders  would  send  the  following  order: 

"Prepare  for  land  defense." 

At  this  command  all  men  of  the  designated  unit  or  units  take  their 
small  arms  and  independently  rush  to  their  positions  previously 
designated  and  prepare  for  land  defense. 

During  artillery  practice  for  batteries  the  fire  commander  is  respon- 
sible to  the  district  commander  for  the  efficiency  of  his  batteries  at 
practice.  His  active  duties  in  connection  with  battery  practice  are 
limited  to  the  preparations  necessary  for  the  highest  efficiency,  and 
to  the  observance  of  safety  precautions  on  the  day  of  the  practice. 

When  a  battery  commander  desires  to  fire  he  requests  authority 
from  the  fire  commander  to  begin;  the  latter  gives  the  authority  if 
the  range  is  safe,  and  the  battery  commander  gives  the  command 
"Commence  Firing"  as  soon  thereafter  as  practicable. 

If  an  interruption  of  the  fire  is  necessary  the  fire  commander  com- 
mands "Cease  Firing."  Firing  is  resumed  after  an  interruption  in 
the  same  manner  as  the  original  firing  was  begun. 


POINTS  FOR  COAST  ARTILLERISTS  501 

The  necessary  precautions  for  safety  are  laid  down  in  the  drill 
regulations.  The  additional  precautions  to  be  observed  during  night 
practice  are  as  follows: 

a.  The  dates  of  the  practice  shall  be  published  so  as  to  reach  with- 
out fail  shipping  and  fishing  interests. 

b.  The  field  of  fire  shall  be  patrolled  before  dark  with  a  view  of 
determining   whether   or  not   vessels   are    anchored    therein    and   of 
warning  approaching  vessels. 

c.  Signal  boats  shall  be  located  so  as  to  observe  any  vessel  approach- 
ing the  range  during  the  firing  and  to  signal  the  battery  firing  by  rocket 
or  other  means. 

d.  At  least  one  searchlight  shall  be  held  on  the  towing  tug  and  one 
on  the  target  during  the  firing. 

e.  The  day  and  hour  of  firing  shall  be  selected  with  a  view  to  having 
the  practice  at  an  hour  when  there  is  least  likelihood  of  a  vessel  crossing 
the  range. 

If  in  the  opinion  of  the  fire  commander  the  deflection  error  of  any 
mortar  shot  is  such  as  to  imperil  the  safety  of  the  field  of  fire,  he  com- 
mands "Cease  Firing"  and  investigates  the  cause  of  error,  indorsing 
results  of  his  investigations  on  the  report  of  the  practice. 

When  troops  are  ordered  for  artillery  practice  away  from  their 
home  stations  they  shall  be  accompanied  by  the  fire  commander  of 
the  fire  command  to  which  they  belong.  This  fire  commander  shall 
require  the  troops  of  his  command  to  be  drilled  carefully  before  the 
practice  begins  at  the  pieces  with  which  such  practice  is  to  be  held. 
He  shall  order  and  supervise  subcaliber  practice  with  each  piece  before 
service  takes  place.  He  shall  assure  himself  before  the  practice 
begins  that  each  gun  and  fire-control  section  is  instructed  sufficiently 
in  the  use  of  the  equipment  furnished  to  derive  the  fullest  possible 
benefit  from  the  practice. 

The  following  rules  are  suggested  to  be  followed  by  safety  officers 
in  charge  of  the  target  practice: 

Vessels  short  of  first  point  of  fall  should  be  considered  in  dangerous 
position  if  within  10  degrees  from  either  side  of  line  of  fire  measured  from 
gun. 

For  all  rounds  where  ricochet  is  expected,  vessels  beyond  first  point 
of  fall  should  be  considered  in  dangerous  position  if  within  45  degrees 
from  line  of  fire  to  the  right,  or  if  within  22^  degrees  from  line  of  fire 
to  the  left,  measured  in  both  cases  from  first  point  of  fall  of  projectile. 

Any  angle  of  elevation  under  9  degrees  may  be  expected  to  give  a 
ricochet. 


502  THE  SERVICE   OF  COAST  ARTILLERY 

For  angles  of  elevation  less  than  9  degrees  the  total  range,  including 
ricochets,  may  be  expected  to  be  at  least  as  great  at  that  given  by  9 
degrees,  and  if  near  9  degrees  probably  greater. 

Based  upon  the  above  assumptions,  the  following  have  been  deter- 
mined to  be  the  required  clear  angles  to  the  right,  measured  from  the 
gun,  for  vessels,  beyond  the  point  of  first  fall  of  projectile,  but  within 
ricochet  range.  These  assume  firings  to  be  with  high-power  guns 
and  full  charges: 

When  first  point  of  fall  is  about  1 ,500  yards  from  gun  the  clear  angle 
from  the  gun  should  be  about  40  degrees.  When  first  point  of  fall  is 
about  4,000  yards  the  clear  angle  should  be  about  30  degrees. 

Where  first  point  of  fall  is  about  8,000  yards  the  clear  angle  should 
be  about  6  degrees  for  an  8-inch  gun  or  less,  about  11  degrees  for  a 
10-inch  gun,  and  about  17  degrees  for  a  12-inch  gun. 

The  clear  angle  to  the  left  should  in  all  cases  be  about  one-half  the 
corresponding  one  to  the  right. 

If  the  conditions  of  water  are  such  that  the  targets  could  be 
towed  at  ranges  of  11,000  yards  there  would  apparently  be  no  danger 
from  ricochet  at  that  range. 


SEARCHLIGHT  COMMANDS 

At  night  the  following  searchlight  commands  are  prescribed  in 
connection  with  battle,  fire  and  mine  lights: 

To  put  occulted  light  into  action  the  command  would  be: 

"No.  1,  In  action." 

To  take  a  light  out  of  action: 

" Battle  (or,  No.  1,  etc.),  Out." 

To  have  a  designated  light  search  its  area,  or  any  sector  of  its  area: 

" Battle  (or,  No.  1,  etc.),  Search  right  (or  middle  or  left)." 

For  a  light  to  search  its  entire  area: 

"Battle  (or,  No.  1,  etc.),  Search." 

If  the  light  is  covering  a  target  the  command  is  "Uncover  and 
Search." 

To  have  a  light  follow  a  target  found  in  its  area: 

"Mine  (or  Battle,  etc.),  Follow." 

To  have  a  light  cover  a  target  already  illuminated  by  another  light : 

"  Battle,  Cover  No.  1,"  or,  "  Mine,  Cover  Battle." 

To  change  a  light  from  one  target  to  another: 

"No.  1,  Uncover  and  cover  Battle." 


POINTS  FOR  COAST  ARTILLERISTS  503 

To  have  a  light  uncover  and  search : 

"No.  4  (or,  Battle,  etc.),  Uncover  and  Search." 

The  command  "Elevate"  means  for  the  controller  operator  to  raise 
the  beam  30  degrees  from  the  horizontal. 

The  command  "Focus'7  indicates  to  the  operator  at  the  light  that 
the  beam  requires  adjusting. 

The  command  "Spread"  means  to  diverge  the  beam. 

The  command  "Contract"  means  to  contract  the  beam. 

Other  commands  used  are:  "Raise,"  "Lower,"  "Raise  slightly," 
"Lower  Slightly,"  "Right,"  "Left,"  "Halt." 

To  indicate  a  target  to  a  battery  at  night,  the  command  would  be: 

"  Dix  (or,  All  batteries) ,  Target  in  Battle  (or,  No.  4,  or  Mine)  beam. 


COMMUNICATION   OFFICER 

No  service  in  the  Coast  Artillery  is  more  important  than  the  accurate 
transmission  and  receipt  of  artillery  communications. 

Communication  officers  should  point  out  to  their  assistants  the 
importance  of  the  duty  which  rests  upon  them.  They  should  person- 
ally instruct  their  subordinates  in  the  proper  method  of  transmitting, 
receiving  and  retransmitting  orders  and  communications. 

They  should  request,  through  their  respective  superiors,  that  men 
detailed  to  this  important  service  at  the  several  stations  in  the  chain 
of  communication  be  selected  with  reference  to  the  following  rules,  viz. : 

1.  General  intelligence. 

2.  Knowledge  of  artillery  terms  and  orders. 

3.  Natural  coolness  and  ability  to  remember  a  message  long  enough 
to  transmit  it  properly. 

4.  Experience  in  the  use  of  the  telephone. 

5.  Ability  to  speak  in  a  modulated  but  distinct  tone  of  voice. 

6.  Familiarity  with  the  English  language  sufficient  to  enable  the 
proper  pronunciation  of  words. 

7.  Complete  absence  of  any  impediment  of  speech  or  foreign  accent. 
Communication   officers  of  fire   commands  are   charged   with  the 

inspection  of  the  equipment  of  the  station  and  the  proper  adjustment 
of  all  instruments  therein. 

When  the  station  is  in  readiness,  the  communiation  officer  reports 
to  the  commander:  "Sir,  Station  in  order." 

He  receives  all  reports  from  batteries  and  transmits  them  to  the 
fire  commander  as  received.  After  all  batteries  in  the  command 


504  THE  SERVICE-  OF  COAST  ARTILLERY 

have  reported  and  upon  intimation  from  the  fire  commander,  he  reports 
to  the  battle  commander,  as  follows: 

"F.  C.  2,  In  order."     (Or  reports  defects  that  cannot  be  repaired.) 

He  communicates  all  orders  from  the  fire  commander  to  the  tele- 
phone operators  on  the  lines  over  which  the  message  is  to  be  transmitted 
and  receives  all  messages  sent  over  such  lines. 

When  a  communication  is  to  one  particular  battery  he  can  facilitate 
its  prompt  and  accurate  delivery  by  personally  transmitting  it  direct 
by  the  use  of  the  cut-off  jack-set. 

When  telephone  operators  have  transmitted  their  messages  word 
for  word  to  the  batteries  to  which  their  lines  are  connected  and  know 
they  have  been  received  correctly,  they  report  to  the  communication 
officer,  as  follows: 

"Dix,  Message  delivered/'     "Richmond,  Message  delivered,"  etc. 

The  expression  "OK"  is  used  by  a  communication  officer  to 
announce  that  a  communication  transmitted  to  him  is  understood. 
To  announce  that  he  has  concluded  a  message  the  letter  "X"  may  be 
used.  For  example,  the  communication  officer  calls  the  operators  in 
communication  with  Batteries  Dix  and  Richmond;  the  operators 
answer,  "Dix,"  "Richmond."  The  communication  officer  then  says: 

"Target,  Side-wheel  steamboat  coming  in.     X." 

The  letter  "X"  in  this  instance  implies  "end  of  message."  It  has 
been  found  that  where  telephone  operators  are  in  booths  they  are  apt 
to  lose  time  in  delivering  messages  by  not  knowing  just  when  the 
message  is  complete.  Accordingly  the  use  of  "X"  at  the  end  of  each 
message  delivered  to  them  signifies  the  end. 

At  the  end  of  the  drill  or  exercise  the  communication  officer,  upon 
intimation  of  the  fire  commander,  sends  the  following  message:  "All 
Batteries,  Close  Stations." 

While  the  above  points  are  for  the  use  of  communication  officers 
detailed  to  fire  commands,  they  are  applicable  to  those  at  battle  com- 
mand stations  as  well. 


BATTERY   COMMANDERS 

To  battery  commanders  the  words  of  the  great  artillerist,  Napoleon, 
apply  with  peculiar  emphasis:  "There  are  no  poor  regiments,  there 
are  some  poor  colonels."  In  other  words,  a  good  battery  commander 
will  always  have  an  efficient  battery. 

Battery  commanders  should  strive  to  obtain  such  a  standard  of 


.     POINTS  FOR  COAST  ARTILLERISTS  505 

discipline  that  the  battery  would  be  able  to  conduct  subcaliber  or 
service  target  practice  in  the  same  orderly  manner  as  they  would  the 
ordinary  routine  drill.  That  is,  the  drills  should  approach  the  con- 
ditions of  actual  service  to  such  a  realistic  extent  that  the  difference 
would  not  be  apparent  to  the  enlisted  personnel. 

The  battery  commander  is  responsible  for  the  excellence  of  the 
gunnery  of  his  command.  This  excellence  is  judged  by  the  accuracy 
and  rapidity  with  which  the  battery  can  hit  the  target.  In  this,  every 
person  who  actually  participates  in  the  firing  has  a  personal  liability; 
the  battery  commander,  the  range  officer,  the  emplacement  officers, 
each  individual  member  of  the  fire-control  section  and  the  gun  detach- 
ments. Only  by  the  united  efforts  of  all  persons  concerned,  working 
in  complete  harmony  with  each  other,  can  the  best  results  be  expected. 
A  failure  in  the  slightest  detail  on  the  part  of  any  one  participating 
may  materially  reduce  the  accuracy  and  rapidity  of  hitting,  and  thus 
defeat  the  efforts  of  the  others  to  attain  the  highest  possible  excellence. 
Success  in  practice,  if  properly  carried  out,  under  as  nearly  as  possible 
service  conditions,  is  by  far  the  best  evidence  of  the  state  of  training 
of  a  company. 

Battery  commanders  are  responsible  for  the  team  work  of  their 
respective  companies,  without  which  it  is  practically  impossible  to 
obtain  results.  They  should  employ  a  system  of  checks  in  order  that 
errors  may  be  located. 

By  personal  inspections  they  should  know  positively  that  the 
military  machine  over  which  they  exercise  command  is  in  proper 
order  and  ready  at  all  times  for  immediate  action. 

Before  artillery  practice  battery  commanders  should  satisfy  them- 
selves that  all  the  material  for  the  practice  is  ready  for  service.  In 
this  connection  the  instructions  contained  in  Coast  Artillery  memoran- 
dum No.  6,  W.  D.  1909,  have  been  copied  without  material  alterations, 
as  follows: 

"...  It  is  believed  that  target  practice  is  a  problem  capable  of 
definite  solution,  within  the  limits  of  accuracy  allowed  by  the  gun  and 
the  ammunition;  but  the  solution  is  arrived  at  only  when  all  the 
variants  or  sources  of  error,  viz.,  ununiformity  in  material  and  methods, 
are  eliminated." 

The  final  objective  of  target  practice  is  to  develop  ability  to  hit. 
To  hit,  or  to  throw  the  projectile  accurately  in  practice  or  in  service, 
we  must  have  for  successive  shots,  uniformity  in  the  several  factors 
that  enter  into  the  problem  of  gun  fire,  viz. : 

(1)  Gun  and  carriage  (action  of). 


506  THE  SERVICE   OF  COAST  ARTILLERY 

(2)  Projectile. 

(3)  Powder. 

(4)  Position -finding  service  (operation  of). 

(5)  Personnel  (work  of). 

The  target-practice  problem,  then,  reduces  itself  to  an  elimination 
of  the  variants  affecting  these  factors. 

1.  Gun  and  Carriage. — Careful  inspection  and  adjustment  will  be 
made  of  the  following: 

(a)  Base  Rings  to  be  Tested  for  Level. — Place  a  clinometer  on  its 
rest  in  the  bore  of  the  gun.  Traverse  the  gun  through  the  field  of  fire, 
recording  variations  in  level  of  the  base  ring  as  indicated  by  the  clinom- 
eter for  azimuths  varying  by  5°.  Calculate,  for  mid-range,  the  range 
corrections  which  should  be  applied  for  variations  in  level,  and  combine 
these  corrections  with  the  corrections  for  gun  displacement;  modify 
the  figures  painted  on  the  base  ring  or  on  the  steps  of  the  loading 
platform  so  that  they  will  represent  the  total  correction  due  to  gun 
displacement  and  variations  in  level. 

In  using  the  clinometer  and  its  rest  the  bore  of  the  gun  should  be 
thoroughly  cleaned  and  any  burrs  on  the  ends  of  the  lands  should  be 
removed  to  facilitate  the  insertion  of  the  adaptors.  The  adjustment 
of  the  clinometer  itself  should  be  tested.  In  giving  the  gun  elevation 
the  last  movement  of  the  elevating  wheel  should  always  be  in  the  same 
direction.  It  will  be  found  that  the  direction  of  this  motion  should 
be  against  preponderance — that  is,  in  the  direction  of  depression. 

(6)  Sight  Standards. — Place  bore  sights  in  the  gun,  and  with  the 
telescopic  sight  on  its  standard,  point  the  gun  so  that- the  line  of  collima- 
tion  of  the  sight  and  the  line  through  the  axis  of  the  bore  intersect  at 
some  well-defined  object  at  or  beyond  mid-range.     For  8-inch,  10-inch, 
and  12-inch  guns  this  adjustment  should  be  made  on  an  object  at  about 
6,000  yards  from  the  gun.     The  sight  itself  should  be  in  adjustment 
and  the  vertical  wire  should  be  in  the  center  of  the  deflection  scale. 

(c)  Quadrant  Elevation  Scales  to  be  tested  for  Adjustment  by  the 
Clinometer  at  0,  5,  and  10  degrees. — The  elevating  pinion  shaft  projecting 
through  the  chassis  rail  carries  one  or  two  disks,  depending  upon  the 
model  of  the  carnage.  There  are  two  scales  on  the  disk  (or  disks), 
one  the  quadrant  elevation  scale,  the  other  the  range  scale.  The 
quadrant  elevation  scale  should  be  tested  by  the  clinometer  and  the 
results  compared  with  the  calibration  record  of  the  battery,  bearing 
in  mind  that  the  index  for  this  scale  may  have  been  adjusted  as  a  result 
of  the  calibration  firing  so  as  not  to  give  the  actual  quadrant  elevation. 
In  the  graduation  of  the  range  scale  allowance  has  been  made  for  the 


POINTS  FOR  COAST  ARTILLERISTS  507 

curvature  of  the  earth  and  the  height  of  the  gun  trunnions.  The 
relation  between  the  graduations  of  the  range  scale  and  the  quadrant 
elevation  scale  is  unalterable.  This  should  be  checked  by  the  battery 
commander,  and  he  should  also  verify  the  computations  upon  which 
these  graduations  are  based  and  the  accuracy  of  graduations  them- 
selves. 

Wear  of  the  elevating  gearing  will  result  in  inaccuracies  at  certain 
parts  of  the  quadrant-elevation  scale.  The  index  should  be  adjusted 
so  as  to  be  correct  for  mid-range  or  for  the  approximate  range  at  which 
trial  and  record  shots  will  be  fired.  In  making  this  adjustment,  as  in 
the  case  of  testing  for  base-ring  level,  the  last  movement  of  the  elevating 
wheel  should  always  be  in  the  same  direction,  viz.,  in  the  direction  of 
depression.  It  is  to  be  noted  that  this  corresponds  to  a  target  coming 
toward  the  battery,  which  will  be  in  the  condition  to  be  expected  in 
the  important  part  of  any  actual  engagement.  With  the  target  going 
away  from  the  battery  it  will  be  found  impracticable  to  have  the  last 
motion  in  laying  the  gun  to  be  that  of  depression,  because  the  gun  must 
be  laid  continuously.  If  all  adjustments  involving  the  elevating 
mechanism  are  made  with  the  last  motion  that  of  depression,  the 
carriage  will  be  in  the  best  adjustment  for  firing  at  a  target  approaching 
the  battery.  It  is  well,  therefore,  at  target  practice,  to  arrange  that 
the  target  shall  approach  the  battery  during  the  firing  of  the  record  shots.. 

(d)  Elevating    Mechanism. — Examine   the    hand-wheel    shaft    and 
bearings,  all  racks  and  pinions,  elevating-rack  slide  and   its  bearing; 
clean  thoroughly  and  oil  all  bearing  parts.     Oil  that  has  accumulated, 
sand  and  grit  should  be  removed.     The  elevating  mechanism  should 
work  easily  and  smoothly  for  both  elevation  and  depression. 

(e)  Friction  Device  of  Elevating  Mechanism  (if  this  device  is  not  in 
proper  adjustment  it  should  be  removed  by  an   ordnance   machinist  and 
examined). — Examine  and  adjust  the  friction  clutch.     The  gun  jumps 
when  it  is  fired.     It  may  be  said  that  correction  for  jump  is  included  in 
correction  made  as  a  result  of  trial  shots;    this  correction,  however, 
will  not  apply  unless  the  jump  is  uniform.     The  proper  adjustment 
of  the  friction  clutch  will  tend  to  make  the  amount  of  the  jump  uniform 
for  successive  shots.     If  the  gun  were  in  a  vise  there  would  be  no 
jump.     We  can  conceive  that  if  the  friction  device  were  so  tight  as 
to  allow  no  movement  in  the  elevating  device  when  the  gun  is  fired,  and 
if  this  device  as  a  whole  were  rigid,  there  would  be  no  j  ump.     The  rigidity 
of  the  mount  in  respect  to  elevation   and   depression  is,   therefore, 
dependent  to  a  degree  on  the  friction  surfaces  of  the  elevating  gearing. 
Jump  should  decrease  with  increased  friction. 


508  THE  SERVICE   OF  COAST  ARTILLERY 

In  making  the  adjustment,  care  must  be  taken  not  to  cause  the  friction 
surfaces  to  bear  too  tight,  otherwise  the  gearing  will  be  endangered. 

The  main  object  is  to  secure  uniformity  in  the  action  of  this  device. 
The  bearings  of  the  elevating  shaft  should  be  kept  clean  and  properly 
lubricated.  The  friction  surfaces  should  be  kept  clean,  smooth,  and 
dry.  They  should  not  under  any  circumstances  be  oiled.  Frequently 
at. drill  elevate  or  depress  to  the  limit  and  turn  the  friction  surfaces  on 
each  other.  According  to  the  Ordnance  Department  pamphlet  the 
elevating  arm  for  12-inch  carriages,  model  of  1896,  should  be  held  by 
friction  surfaces  only  so  tight  as  will  prevent  the  elevating  arm  sliding 
down. 

(/)  Traversing  Mechanism. — Examine  the  crank  shaft  and  the 
bearings,  all  racks  and  pinions;  clean  thoroughly  and  oil  all  bearing 
parts  of  the  traversing  mechanism.  Clean  traversing  rollers  and  their 
paths,  and  oil  all  bearing  surfaces  as  often  as  necessary.  Different 
sections  of  the  dust  guards  should  be  removed  each  month  of  the  out- 
door season. 

(g)  Recoil  Cylinders  (to  be  cleaned  and  filled,  periodically,  as  required 
by  Ordnance  Department  pamphlet  for  the  carriage  considered). — The 
follower  should  not  be  so  tight  as  to  cause  undue  friction,  nor  so  loose 
as  to  allow  leakage.  (See  C.  A.  D.  R.  instructions  for  packing  stuffing 
boxes  and  adjusting  followers.)  The  adjustment  of  glands  and  fol- 
lowers must  be  uniform  for  the  two  cylinders.  Examine  the  cylinders 
just  before  firing  to  see  that  they  are/w/Z. 

(h)  Recoil  and  Counter-Recoil  System. — Clean  crossheads  and  guides, 
recoil  rollers,  upper  and  lower  roller  paths,  and  lubricate  all  bearings. 
For  firing;  rollers,  paths  and  piston  rods  should  be  bright  and  slightly 
lubricated  with  thin  oil.  Keep  grease  cups  full  and  so  adjusted  that 
they  function  properly  at  all  times.  The  gun  should  be  tripped  fre- 
quently and  time  of  going  into  battery  recorded  with  a  view  to  observ- 
ing whether  or  not  the  action  of  the  carriage  is  uniform.  Equalizing 
pipes  must  be  clean  and  free  from  "settlings"  or  solid  matter,  so  as  to 
allow  a  free  circulation  of  oil.  Throttling  valves  should  be  properly 
set  by  reference  to  records  as  to  action  of  the  carriage  with  settings  at 
previous  times,  or  as  judgment  and  experience  may  dictate.  The 
setting  of  the  valve  depends  principally  upon  the  temperature  of  the 
oil  in  the  cylinders  at  the  time  of  firing.  The  records  of  previous  firings, 
therefore,  should  show  the  setting  of  the  valve,  the  amount  of  recoil, 
temperature  of  the  oil  in  the  cylinders,  and  the  time  elapsing  between 
successive  shots.  It  should  be  noted  whether  or  not  with  the  same 
setting  the  recoil  increases  with  shots  fired  at  short  intervals. 


POINTS  FOR  COAST  ARTILLERISTS  509 

(i)  Breechblocks  and  Obturators. — Once  a  month  breechblocks  should 
be  dismantled  and  all  parts  carefully  cleaned.  Cable  and  breech  con- 
tacts will  be  freed  of  all  grease  and  dirt.  Dummy  pressure  plugs  will  be 
unscrewed  occasionally  and  threads  of  pressure-plug  recesses  examined. 
Prior  to  practice  cylinders  for  pressure  plugs  will  be  measured,  and 
gun  commanders  will  be  instructed  in  the  preparation  of  the  plugs  and 
their  use  during  practice. 

Adjust  the  obturator  so  that  a  slight  effort  will  be  required  to  turn 
the  mushroom  head.  See  that  the  gas-check  pad  is  serviceable. 

(j)  Firing  Attachments. — Examine  firing  attachment.  Take  it  apart 
occasionally  and  clean  it;  oil  its  bearing  parts  so  that  it  functions  easily. 
Men  should  be  instructed  to  insert  the  primer  by  pushing  on  the  body 
of  the  primer  and  not  on  the  button  wire.  The  slide  must  be  lowered 
completely  down.  If  a  primer  fails,  its  button  wire  should  be  bent  back 
over  the  body  of  the  primer,  so  that  the  primer  will  not,  by  mistake,  be 
inserted  again  during  the  firing.  In  bending  the  wire  back  care  should 
be  taken  to  put  as  little  strain  as  possible  on  the, button  wire  in  the 
direction  of  the  axis  of  the  primer  body,  to  avoid  the  possibility  of 
igniting  friction  composition  in  the  primer. 

See  that  the  safety  lanyard  is  in  working  order,  if  this  is  used;  and 
test  all  lanyards  to  see  that  they  are  strong  and  serviceable. 

(k)  Azimuth  Subscales  (Mortars). — Check  up  the  data  upon  which 
orientation  of  mortars  is  based  and  verify  the  setting  of  azimuth  sub- 
scales  before  practice.  (See  Method  of  orienting,  in  chapter  X,  also 
in  D.  R.)  Having  once  verified  the  orientation  data,  setting  of 
azimuth  subscales  can  be  readily  checked  by  a  transit  on  the  parapet 
or  in  rear  of  the  pit.  By  means  of  bore  sights  direct  the  vertical  wire 
of  the  transit  on  the  axis  of  the  bore  and,  if  necessary,  move  the  sub- 
scale  so  that  it  indicates  the  correct  azimuth  reading.  The  subscale 
should  be  doweled  in  position  when  correctly  set.  Station  for  the 
transit  should  be  located  at  a  point  near  the  battery  from  which  all 
mortars  are  visible  and  correct  data  for  this  point  determined.  The 
orientation  of  the  B.  C.  instrument  and  instruments  in  P.  F.  system 
must  agree  with  that  of  the  mortars.  An  azimuth  instrument  may 
be  used  for  this  adjustment  if  a  transit  is  not  available. 

(1)  Quadrants  (Mortars). — Test  and  adjust  all  quadrants.  Expan- 
sion and  contraction  due  to  sun  and  shade  make  it  difficult  to  keep 
quadrants  in  adjustment.  They  should  be  tested  with  the  clinometer 
as  short  a  time  before  firing  as  possible.  As  the  clinometer  does  not 
read  to  45°  and  the  quadrant  does  not  read  below  45°,  an  old-style 
quadrant  may  be  placed  on  the  surfaces  prepared  for  it  at  the  breech 


510 


THE   SERVICE    OF   COAST   ARTILLERY 


and  its  zero  determined  by  the  clinometer.  Having  adjusted  this 
quadrant  the  attached  quadrant  should  be  compared  with  it  at  eleva- 
tions differing  by  5°  between  45°  and  70°. 

(m)  Adjust  sights  to  remove  parallax  and  for  clear  definition. 
(See  Adjustment  of  telescopes.) 

(n)  Ammunition  Trucks  (See  Fig.  87).— Oil  -axles.  Have  trays 
clean  and  smooth.  Trucks  for  disappearing  carriages  should  be 


FIG.  87. — Emplacement  Booth,  Equipment,  and  Ammunition  Truck. 

adjusted  approximately  for  proper  height  of  breech  in  loading  position 
just  before  practice.  Tray-elevating  and  depressing  mechanism  must 
be  lubricated  and  should  be  frequently  operated. 


IN  GENERAL. 

The  bore  and  chamber,  breechblock,  and  all  parts  of  the  carriage, 
such  as  traversing  rollers  and  their  paths,  and  crosshead  guides,  will 
be  carefully  freed  of  grease  and  dirt;  only  bearing  surfaces  should  be 
lubricated. 

Uniformity  in  the  action  of  the  gun  and  carriage  will  be  attained 
by  lubrication  of  bearing  surfaces  and  by  adjustment  of  the  working 
parts  of  the  gun  and  carriage  to  insure  smooth  operation  of  the  whole 


POINTS  FOR  COAST  ARTILLERISTS  511 

as  a  machine,  (iuns  should  be  tripped  and  retracted  frequently. 
Just  before  target  practice  this  should  be  done  several  times  a  day. 
The  action  of  guns  and  carriages  in  firing  should  be  observed,  and  a 
careful  inspection  should  be  made  of  them  before  and  immediately  after 
firing,  notation  being  made  of  any  change  in  adjustment  as  well  as  of 
any  defects  in  material  that  the  firing  has  caused. 

2.  Projectiles. — The  weights  of  all  projectiles  to  be  used  in  a 
practice  will  be  adjusted  as  nearly  as  possible  to  standard -range  table 
weights.  This  may  be  done  by  filling  the  cavities  of  the  projectiles 
with  sand.  A  difference  in  weight  of  less  than  2  pounds  may  be 
neglected,  but  anything  greater  than  this  should  be  taken  into  account. 

Remove  all  loose  paint  from  projectiles,  making  their  surfaces 
smooth;  polish  the  bourrelets. 

The  rotating  bands  will  be  carefully  cleaned  and  all  oil  and  grit 
removed  from  the  grooves.  Burrs  on  rotating  bands  or  bourrelets 
will  be  removed. 

Rotating  bands  of  projectiles  will  be  calipered  and  the  projectiles 
classified  in  groups  so  that  all  projectiles  for  trial  shots  and  all  for 
record  shots  will,  if  possible,  have  rotating  bands  of  the  same  diameter. 
In  order  that  this  work  may  have  any  value  it  must  be  done  most  care- 
fully. 

Variations  in  diameters  of  rotating  bands  cause  variations  in 
velocities.  The  grouping  of  projectiles,  therefore,  according  to  diameters 
of  rotating  bands  will  permit  of  uniform  projectiles  being  used  for  trial 
and  for  record  shots,  and  differences  in  velocities  between  the  pro- 
jectiles  used  for  trial  and  those  used  for  record  shots,  due  to  ununiform 
rotating  bands,  can  be  allowed  for. 

It  has  been  determined  by  careful  experiment  that  the  variation 
of  4-0.025  of  an  inch  in  the  diameter  of  a  rotating  band  of  a  6-inch 
projectile  has  given  an  increase  of  30  f.  s.  in  velocity.  The  Ordnance 
Department  specifications  allow  a  variation  of  ±0.003  of  an  inch  in 
diameter  of  rotating  bands. 

At  all  practices  keep  records  as  to  differences  in  diameters  of  rotating 
bands  of  projectiles  for  trial  shots  and  corresponding  range  variations. 
If  all  other  variants  have  been  eliminated  in  the  trial  shots,  the  informa- 
tion to  be  obtained  from  these  records  will  be  of  assistance  to  battery 
commanders  in  making  allowances  for  velocity  due  to  differences  in 
rotating  bands. 

The  Ordnance  Department  last  year  conducted  experiments  with 
projectiles  with  narrow  rotating  bands  at  a  battery  the  guns  of  which 
had  been  fired  200  times.  The  projectiles  with  narrow  bands  fell  very 


512  THE  SERVICE   OF  COAST  ARTILLERY 

erratically.  Projectiles  with  similar  bands  fired  from  new  guns  gave 
normal  results.  The  Ordnance  Department  has  issued  projectiles 
with  broad  rotating  bands  for  use  at  some  of  the  batteries  whose 
guns  are  known  to  be  considerably  worn.  (The  guns  of  two  such 
batteries  have  been  fired  200  times,  and  the  third  118  times.)  It  is 
hoped  that  these  broad-banded  projectiles  will  increase  the  accuracy 
of  guns  that  have  been  fired  a  great  number  of  times. 

NOTE. — Firing  with  broad-banded  projectiles  of  the  new  design 
has  been  recently  conducted.  The  results  of  this  firing  were  most 
satisfactory;  the  dispersion  of  shots  in  calibration  firing  was  small, 
and  in  the  record  firing  100  per  cent,  of  hits  was  made. 

3.  Powder. — Powder  for  heavy  guns  (except  those  using  fixed 
ammunition)  will  be  blended  as  described  in  chapter  VI.  After  blending 
the  sections  of  charges  will  be  carefully  made  up.  Each  section  should 
be  as  stiff  and  rigid  as  possible,  and  of  uniform  cross-section  and  length. 
This  can  be  attained  by  care  in  relacing  and  by  a  process  of  kneading  or 
rolling  after  lacing.  Weights  of  powder  charges  will  be  verified  by  an 
officer.  The  following  illustration  indicates  very  conclusively  the 
advantage  of  careful  blending.: 

Last  year  several  practices  were  held  at  a  battery  of  12-inch  rifles 
on  disappearing  carriages,  with  International  Lot  No.  9,  1907,  powder. 
This  powder  was  carefully  blended  and  behaved  with  great  uniformity 
at  all  practices.  The  powder  appeared  to  be  weak,  however,  and  on 
this  account  the  Ordnance  Department  sent  four  charges  of  the  same  lot 
to  be  tested  for  initial  velocity.  Two  charges  slightly  under  normal 
weight  gave  the  following  results : 

First  shot I.  V.  2,153  f.  s. 

Second  shot I.  V.  2,206  f.  s. 

Variation 53  f.  s. 

Two  charges  slightly  over  normal  weight  gave — 

First  shot I.  V.  2,369  f.  s. 

Second  shot I.  V.  2,320  f.  s. 

Variation 49  f.  s. 

These  charges  were  tested  as  shipped  from  the  arsenal  and  were 
not  blended. 

Five  charges  of  the  same  lot  of  powder  were  blended  and  shipped 
for  test.  These  charges  were  blended  with  16  other  charges  which 


POINTS   FOR  COAST  ARTILLERISTS  513 

were  used  in  practice.     The  results  obtained  with  the  five  blended 
charges  were  as  follows: 

First  shot I.  V.  2,198  f.  s. 

Second  shot I.  V.  2,202  f.  s. 

Third  shot I.  V.  2,212  f.  s. 

Fourth  shot I.  V.  2,203  f.  s. 

Fifth  shot I.  V.  2,215  f.  s. 

Maximum  variation 17  f.  s. 

The  Ordnance  Department  specifications  for  powder  allow  a  varia- 
tion of  1  per  cent,  either  way  from  normal  velocity.  For  a  powder  with 
normal  muzzle  velocity  of  2,250,  it  will  be  seen  that  the  total  allowable 
variation  is  45  f.  s. 

4.  Position-Finding  Service. — Communications  will  be  inspected 
and  all  instruments  in  the  position-finding  service  will  be  put  in  a  con- 
dition of  minimum  error.  Check  all  data  upon  which  the  position- 
finding  system  is  based  by  examination  of  all  available  records  and 
calculations  of  involved  triangulations,  if  necessary. 

(a)  Depression  Position  Finder. — Test  position  finder  for  adjustment 
and  orientation.  Instruct  observer  in  the  proper  use  of  instrument  to 
avoid  errors  due  to  lost  motion.  Where  targets  entering  the  harbor 
move  across  the  field  of  fire  in  the  same  direction  during  their  entire 
course,  azimuth-reading  instruments  should  be  adjusted  by  bringing  the 
vertical  wire  on  the  orientation  point  always  in  the  same  direction,  which 
direction  should  be  that  of  the  target  in  entering  the  harbor.  Where 
lost  motion  exists  which  cannot  be  eliminated,  its  effect  should  be 
carefully  ascertained  and  corrected  for  by  the  reader,  especially  when  the 
direction  of  motion  of  the  target  which  is  being  followed  is  opposite  to 
that  used  in  adjusting  the  instrument  on  the  orientation  point.  It  is 
very  important  that  the  observer  should  be  instructed  to  stop  the 
instrument  on  the  last  stroke  of  the  bell,  and  in  order  to  do  this  he  must 
keep  the  vertical  wire  exactly  on  the  designated  point  of  the  target 
during  the  last  two  or  three  seconds  of  the  interval.  Similarly  the 
horizontal  wire,  in  using  the  instrument  for  determining  ranges,  must 
be  stopped  on  the  water  line  on  exactly  the  last  stroke  of  the  bell. 
Observers  should  be  trained  to  give  particular  attention  to  either  the 
vertical  or  the  horizontal  wire  during  the  last  seconds  of  each  observing 
interval,  depending  upon  whether  the  azimuth  or  the  range  of  the  target 
is  changing  most  rapidly.  If  the  azimuth  is  changing  more  rapidly 
than  the  range,  the  last  two  or  three  seconds  should  be  devoted 


514  THE  SERVICE   OF  COAST  ARTILLERY 

exclusively  to  the  setting  of  the  vertical  wire.  If  the  range  is  changing 
more  rapidly  than  the  azimuth,  the  last  two  or  three  seconds  of  each 
interval  should  be  devoted  exclusively  to  the  setting  of  the  horizontal 
wire. 

(b)  Plotting  Board. — Check  orientation  of  base  line  and  numbering 
of  the  degrees  on  the  azimuth  circle.     Verify  the  setting  of  the  gun 
center.     See  that  the  locks  and  all  mechanical  devices  are  in  adjustment. 
To  avoid  errors  due  to  lost  motion  in  setting  arms,  both  arm  setters  and 
the  plotter  should  be  instructed  to  cause  the   last  motion  of   arms  to 
be  always  in  the  same  direction.     The  proper  operation  of  these  arms 
requires  skill  and  care.     A  determination  of  maximum  and  minimum 
errors  that  result  from  various  methods  of  setting  arms,  at  different 
positions  on  the  board,  will  impress  upon  the  plotting  detachment  the 
importance  of  uniformity  in  the  setting  of  arms.     The  calculated  and 
plotted  ranges  (the  latter  by  the  method  of  setting  arms  selected  as 
being  most  accurate)  should  not  differ  by  more  than  10  yards  at  mid- 
range.     When  the  course  of  the  target  is  plotted  it  should  show  uniform 
intervals,  either  equal  or  uniformly  increasing  or  decreasing,  depending 
upon  its  speed.     If  the  interval  suddenly  changes  the  plotter  reports 
the  fact  to  the  range  officer.     The  latter  immediately  looks  for  "the 
trouble  and  takes  steps  to  eliminate  it. 

(c)  Range  Board. — The  ruler  should  be  parallel  to  the  range  lines. 
There  should  be  no  lateral  motion  of  the  ruler.     The  string  should  be 
properly  centered.     Some  trouble  has  been  experienced  in  the  use  of 
range  boards  due  to  the  fact  that  with  the  old  type  of  range  charts  the 
velocity  curves  did  not  cover  the  low  velocities  developed  in  practice. 
Some  officers  constructed  additional  curves  in  pencil  and  some  selected 
arbitrarily  a  curve  on  the  chart  and  made  an  additional  range  correction 
on  the  range  arm.      The  latter  method  is  inaccurate  when  trial  shots 
and  record  shots  are  fired  at  different  ranges  and  should  not  be  used. 
It  is  not  expected  that  these  difficulties  will  arise  this  year,  since  the 
Ordnance  Department  has  issued  the  latest  revised  range  charts  with 
velocity  curves  from  2,100  f.  s.  to  2,400  f.  s.,  to  all  heavy  gun  batteries. 
If,  however,  velocities  fall  below  the  curves  on  the  range  board,  addi- 
tional curves  in  pencil  should  be  constructed. 

The  following  directions  in  the  use  of  range  boards  should  be  observed 
where  they  apply: 

On  range  boards  issued  prior  to  December  26,  1906,  the  curves 
are  constructed  to  give  corrections  for  the  actual  range.  Therefore,  it 
is  necessary  that  the  operator  of  the  board  should  keep  the  ruler  set 
at  the  actual  range  and  not  the  corrected  range.  A  setting  to  within 


POINTS  FOR   COAST  ARTILLERISTS  515 

100  yards  of  the  actual  range  is  sufficiently  accurate.  The  operator 
should  be  drilled  in  obtaining  approximately  the  actual  ranges  from 
the  corrected  ranges  read  by  the  plotter  from  the  gun  arm  of  the  plotting 
board. 

On  range  boards  issued  December  26,  1906,  and  subsequently,  the 
curves  are  constructed  to  give  the  correction  for  the  corrected  ranges, 
to  that  ranges  read  from  the  gun  arm  of  the  plotting  board  should  be 
used  in  setting  the  ruler.  The  first  corrected  range  can  be  obtained 
only  by  using  the  actual  range  in  setting  the  ruler,  hence  it  is  only  an 
approximation.  The  second  corrected  range  obtained  by  setting  the 
ruler  at  the  first  corrected  range  will  be  sufficiently  accurate  to  use  for 
firing.  It  is  necessary  to  obtain  the  second  corrected  range  in  firing  at  a 
stationary  target  as  well  as  at  a  moving  target. 

(d)  Deflection  Board. — See  that  the  proper  leaf-range  scale  and  T- 
square  range  scale  are  attached  and  that  the  board  is  otherwise  in 
adjustment. 

Examine  time-interval  clock,  interrupter,  and  bell,  and  all  telephones 
and  switches,  to  see  that  they  are  in  good  working  order  and  properly 
adjusted.  See  that  all  screws  are  tight. 

5.  •  Personnel. — Substitutes  should  be  trained  for  all  the  important 
positions  in  order  that  unexpected  vacancies  may  be  filled.  All  men 
operating  telephones  or  other  instruments  will  be  put  through  the  proper 
operators'  tests,  and  drilled  with  a  view  to  eliminating  personal  errors. 
Too  great  attention  cannot  be  given  to  the  minutest  details.  Each  day 
the  drill  should  be  conducted  as  in  target  practice,  or  as  if  the  boat  for 
drill  represented  the  enemy.  At  least  once  a  week  a  simulated  target 
practice  should  be  conducted  at  each  post.  Time-out  will  be  given 
occasionally  as  in  practice.  Any  errors  that  are  brought  out  in  these 
simulated  practices  will  be  investigated  and  eliminated.  Such  records 
should  be  kept  as  will  permit  of  careful  checking  of  the  work  of  each 
individual  of  the  personnel  throughout  the  system.  The  training  of 
the  personnel  should  be  progressive;  from  the  individual  to  the 
detachment,  and  then  to  the  battery.  The  work  of  the  battery  as  a 
unit  requires  co-ordination  of  the  work  of  the  various  detachments. 
The  individual  training  of  gun  pointers  should  be  given  attention. 

The  range  officer  is  responsible  for  the  accuracy  of  the  data  trans- 
mitted from  the  plotting  room  to  the  guns.  He  in  turn  should  hold  the 
plotter  responsible  for  errors  that  pass  him  undetected.  As  a  check 
against  errors  in  deflection  the  gun  pointer  should  be  taught  to  associate 
the  value  of  deflections  sent  to  him  with  the  angular  travel  of  the  target, 
which  is  uniform,  or  increasing  or  decreasing  at  a  uniform  rate.  It  is 


516 


THE   SERVICE   OF   COAST   ARTILLERY 


thought  that  a  gun  pointer  can  be  readily  trained  to  detect  errors  in 
deflections  when  the  fact  is  impressed  upon  him  that  their  values  should 
be  uniform  or  increasing  or  decreasing  at  a  uniform  rate. 

Dummy  projectiles  (see  Fig.  88)  should  be  rammed  with  the  same 
energy  as  would  be  employed  in  practice.  Ramming  a  very  few  pro- 
jectiles during  the  drill  will  be  of  more  value  than  going  through  the 
motions  any  number  of  times.  Uniform  ramming  is  of  the  greatest 
importance.  If  the  projectile  is  not  well  rammed  the  powder  gas  will 


FIG.  88. — Complete  Dummy  Charge  for  12-inch  Gun. 

escape  around  the  rotating  band,  and  there  will  be  a  loss  in  velocity. 
Projectiles  should  be  rammed  with  all  force  possible. 

It  has  been  determined  by  test  that  the  variation  of  a  few  tenths 
of  an  inch  in  the  seating  of  a  projectile  will  give  a  variation  of  70  f.  s. 
in  muzzle  velocity,  due  to  the  fact,  apparently,  that  powder  gases 
escape  around  the  rotating  band.  The  velocity  in  the  case  of  the 
projectile  not  being  home  is  less  than  when  the  projectile  is  rammed 
well  home.  (See  Fig.  89.) 

The  following,  bearing  on  the  training  of  the  personnel,  is  taken 


POINTS  FOR  COAST  ARTILLERISTS 


517 


from  a  report  of  an  officer  of  the  Coast  Artillery  Corps,  who  has  secured 
uniformly  good  results  in  practice : 

"The  adjustment  of  the  gun  and  carriage  and  the  preparation  of 


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the  ammunition,  etc.,  is  done  before  firing,  when  there  is  ample  time 
for  verification,  but  the  accuracy  of  the  work  of  the  personnel  is 
practically  beyond  the  control  of  the  battery  commander  after  firing 
once  begins.  This  must  be  provided  for  by  thorough  training.  In  this 


518  THE   SERVICE   OF  COAST   ARTILLERY 

training  the  methods  of  work  used  by  each  member  of  the  range  detach- 
ment including  the  range  keeper  and  gun  pointer  should  be  definitely 
prescribed  ....  The  sequence  in  which  each  member  of  the  detach- 
ment performs  the  details  of  his  work  should  be  prescribed,  also  as  far 
as  possible  the  mental  process  he  uses.  The  drill  should  then  be 
continued  until  the  work  of  each  member  becomes  mechanical  and 
thus,  by  force  of  habit,  reduce  to  a  minimum  the  errors  that  may  occur 
when  working  under  conditions  of  excitement  or  fatigue. 

"In  developing  the  work  of  the  range  detachment,  I  worked  at 
each  position  in  the  detachment  until  I  was  thoroughly  familiar  with 
the  details  of  the  work  at  each  position.  I  noted  the  routine  in  which 
each  step  of  the  work  could  best  be  done,  and  where  errors  were  likely 
to  occur.  I  also  noted  where  irregularities,  such  as  the  loss  of  one  or 
more  observations,  an  error  in  reading  the  range  or  azimuth,  etc., 
were  likely  to  occur  and  prescribed  exactly  what  should  be  done  in  each 
case,  and  by  whom  the  correction  of  an  error  should  be  made.  I  then 
prescribed  in  detail  the  methods  to  be  used  at  each  position  and 
required  that  they  be  strictly  followed. 

"If  observations  are  lost,  the  plotter  should  so  inform  the  guns. 
In  case  of  errors  in  the  observations  or  in  the  setting  of  the  arms,  he 
should  report  "lost"  to  the  guns,  unless  it  can  be  at  once  corrected. 
In  both  cases  the  range  keeper,  having  noted  the  rate  of  change  in 
range  from  previous  data,  should  be  able  to  set  the  disk  at  approximately 
the  correct  range  and  continue  to  do  so  for  several  observations. 
In  transmitting  the  deflection  to  the  guns  the  plotter  should  not 
attempt  to  detect  errors  therein,  as  he  is  fully  occupied  with  his  other 
work. 

"The  correctness  of  the  work  of  the  range  detachment  should  be 
continually  verified  at  all  drills.  If  errors  occur,  they  should  be 
traced  to  the  members  of  the  detachment  making  them  and  the  cause 
for  same  determined  and  corrected.  The  rate  of  change  in  the  corrected 
range  at  which  the  range  disk  will  be  set  will  be  uniform  or  gradually 
increasing  or  decreasing,  depending  upon  the  course  and  speed  of  the 
target.  A  record  of  the  actual  settings  of  the  range  disk  will  indicate 
in  a  general  way  the  accuracy  of  the  work  of  the  range  detachment 
as  a  whole. 

"The  following  method  is  useful  in  verifying  the  work  of  each 
member  of  the  range  section  except  the  observers  and  readers: 

"Prepare  data  corresponding  to  the  track  of  a  target  having  both 
change  in  range  and  angular  travel.  This  should  be  sufficient  to  cover 
about  one-half  hour  of  tracking.  With  the  plotting  board,  range  board, 


POINTS   FOR   COAST  ARTILLERISTS  519 

etc.,  determine  the  following  for  each  observation  and  tabulate  same  in 
convenient  form: 

"Number  of  observation. 

"  If  vertical  base  is  used :  Azimuth  of  the  target  from  B' ;  range  of 
the  target  from  B'. 

"  If  horizontal  base  is  used:  Azimuth  of  the  target  from  B';  azimuth 
of  the  target  from  B". 

"  Corrected  range  sent  to  the  guns. 

"  Angular  travel. 

"Total  range  correction  as  applied  on  range  correction  scale. 

"  Deflection. 

"Corrected  range  (corrected  for  gun  displacement)  for  each  gun  of 
the  battery  except  the  directing  gun. 

"The  azimuth  of  the  target  from  B'  and  B"  or  the  azimuth  and 
range  from  B',  if  a  vertical  base  is  used,  as  given  in  above  data,  should 
be  transmitted  from  the  proper  observing  station  to  the  plotting 
room  at  the  usual  observing  intervals.  The  work  of  the  range  section 
and  gun  detachment  should  proceed  in  the  usual  manner.  A  record 
of  the  work  of  each  member  of  the  detachment,  corresponding  to  that 
noted  above,  should  be  made  and  should  include  the  actual  settings 
of  the  range  disk  of  each  gun  and  the  actual  setting  of  each  sight  for 
deflection.  A  comparison  with  the  prepared  data  will  show  all  errors. 
To  test  the  plotter  as  to  the  detection  of  errors  in  observations, 
reading,  etc.,  incorrect  azimuths  or  ranges  should  occasionally  be 
transmitted  from  the  observing  room.  The  plotter  should  detect 
these  and  call  "lost"  to  the  guns.  Occasionally  the  data  for  one  or 
more  observations  should  be  regarded  as  lost  and  not  sent  to  the 
plotting  room.  The  range  keeper  should  have  kept  the  range  disk 
set  at  the  proper  range  from  data  previously  sent,  as  above  explained. 
The  records  of  the  actual  setting  of  the  range  disk  will  show  with  what 
accuracy  this  has  been  done. 

"  Occasionally  an  incorrect  range  or  deflection  should  be  sent  from 
the  plotting  room  to  the  guns  for  the  purpose  of  testing  the  range 
keepers  and  gun  pointers. 

"The  above  method  can  be  used  to  advantage  when  there  are  no 
targets  in  the  field  of  fire  or  it  is  foggy." 

Variations  in  Muzzle  Velocity. — The  battery  commander  should 
know  what  variation  in  muzzle  velocity  can  be  attributed  to  certain 
conditions  which  may  exist  in  a  practice.  Variation  in  range  due  to 
a  given  variation  in  muzzle  velocity  and  atmospheric  conditions  can  be 
taken  from  the  range  board.  Variations  in  muzzle- velocity  due  to 


520  THE   SERVICE   OF   COAST   ARTILLERY 

variations  in  weights  of  charges,  diameters  of  rotating  bands,  length  of 
travel  of  a  projectile  in  the  bore,  and  to  improper  seating  of  projectiles 
in  the  gun  cannot  be  taken  from  range  tables;  and  variations  in  range 
due  to  variations  in  weights  of  projectiles  cannot  be  taken  directly 
from  these  tables.  The  following  formulae  are  reasonably  accurate 
for  small  variations  in  weights  of  projectiles  and  powder  charges  and 
variation  of  travel  of  shot  in  the  bore: 

Variation  in  velocity  due  to  variation  in  weight  of  projectile: 

A  V  =  — —  -   -  V  ,  in  this  formula  w=  weight  of  projectile. 

Variation  in  velocity  due  to  variation  in  weight  of  charge: 

6  Aw 

A  V  =—      —  V  ,  in  which  w=weight  of  charge. 
5    w 

In  these  formulae  weights  of  projectiles  and  powder  charges  are  to 
be  taken  in  pounds  and  length  of  travel  in  inches.  The  effect  of  the 
length  of  travel  alone  can  usually  be  neglected,  though  some  battery 
commanders  may  be  interested  in  accounting  for  it. 

To  illustrate  the  effect  of  only  two  variables,  let  us  take  the  follow- 
ing simple  example: 

The  12-inch  rifle,  model  1888,  fires  three  trial  shots  at  a  range  of 
6,000  yards  at  a  fixed  target.  The  normal  velocity  is  2,520.  Weight 
of  projectile,  normal,  1,046  pounds.  Weight  of  charge,  normal,  275 
pounds.  The  projectile  for  the  first  trial  shot  weighs  1,058  pounds. 
The  projectile  for  the  second  shot  weighs  the  same.  The  third  pro- 
jectile has  normal  weight  (1,046  pounds). 

The  charge  for  the  first  shot  weighs  275  pounds.  The  charge  for  the 
second  shot  weighs  275  pounds.  The  weight  of  the  charge  for  the 
third  shot  is  276  pounds. 

Assuming  that  there  are  no  other  variations  in  projectiles  and 
powder,  in  the  work  of  the  personnel,  or  in  the  operation  of  the  gun 
and  carriage,  what  would  be  the  difference  in  range  between  the  1st 
and  3d  trial  shots? 

By  the  formulas  above,  we  find  that  the  variation  in  velocity  due 
to  +12  pounds  difference  in  weight  of  projectiles  is  —11.29  f.  s.,  and 
that  the  variation  in  velocity  due  to  variation  of  + 1  pound  in  weight  of 
powder  charge  is  +9.8  f.  s. 


POINTS  FOR  COAST  ARTILLERISTS 
Therefore,  we  have— 


521 


No.  of  Shot. 

Weight  of 
Projectile. 

Pounds. 

Weight  of 
Charge. 

Pounds. 

Variation 
in  Muzzle 
Velocity, 
f.  s. 

Range 
Variation. 

Yards. 

Range 
Attained  . 

Yards. 

1  
2 

1058 
1058 

275 

275 

-11.29 
-11.29 

-50.8 
-50.8 

5,949.2 
5,949.2 

3  

1046 

276 

+   9.81 

+  45.1 

6,045.1 

The  difference  in  range  between  first  and  third  trial  shots,  there- 
fore, would  be  95.9  yards. 

This  shows  the  effect  of  the  combination  of  only  two  varying 
factors.  A  systematic  elimination  of  all  variables  which  may  be 
said  to  be  in  the  hands  of  the  battery  commander  is  necessary  if  the 
problem  is  to  be  solved  with  any  certainty.  It  is  possible  that  in 
practices  where  good  results  have  been  obtained  there  have  been 
compensating  variations.  Success  in  these  cases  has  been  due  to 
good  luck,  not  good  management.  Good  practice  on  the  average  will 
result  only  from  methodical  and  painstaking  work  at  all  times. 

Accuracy  of  Fire  and  Practice. — Battery  commanders  should  dis- 
tinguish between  accuracy  of  fire  of  a  gun  and  accuracy  of  practice  of 
a  gun.  Accuracy  of  fire  is  determined  by  the  grouping  of  shots  around 
the  center  of  impact  of  the  group.  Accuracy  of  practice  is  determined 
by  the  distance  of  the  center  of  impact  from  the  center  of  the  target. 
In  order  to  have  a  measure  of  accuracy  of  fire,  and  of  practice,  battery 
commanders  should  know  the  probable  errors  of  the  guns  of  their 
batteries  with  the  ammunition  used  in  practice.  All  shots  of  the  group 
of  shots  from  which  the  probable  error  is  determined  should  be  fired 
at  the  same  elevation  and  under  identical  conditions  as  nearly  as 
possible. 

In  order  to  have  available  information  as  to  probable  errors  of 
their  guns,  data  will  be  collected  from  trial  and  calibration  shots  from 
the  guns  of  each  battery.  For  this  purpose,  district  commanders 
have  issued  a  number  of  blank  probable  error  cards  of  the  type 
shown  on  page  522,  sufficient  for  carrying  out  the  instructions  indi- 
cated. 


522 


THE   SERVICE   OF  COAST   ARTILLERY 


Probable  error  card. 


Battery 

Company Post 


District 
Date  . 


G 

Ul 

•s  . 

CARRIAGE. 

Caliber. 

Model. 

Reg.  No. 

Tact.  No. 

Kind.                 Model.              Reg.  No. 

No.  of 
Round. 

Serial 
No.  from 
Piece. 

Range. 

Yards. 

Difference 
from  Mean 

Remarks. 

Sum 

Mean  

(Mean  error  X 0.845=  probable  error.) 
Probable   error yards.     Expectation 


per   centum    of   hits. 


Each  battery  commander,  and  ordnance  officers  of  batteries  out 
of  commission,  will  determine  and  record  on  the  probable  error  card 
the  probable  error  and  expectation  of  hits  from  each  group  of  shots 
from  each  gun  fired  at  the  same  elevation,  viz.:  Trial  shots  fired  just 
before  target  practice,  and  calibration  shots. 

Battery  commanders  will  enter  on  probable  error  cards  each  group 
of  trial  and  calibration  shots,  going  as  far  back  as  the  records  of  practice 
of  their  batteries  show  groups  of  three  or  more  shots  fired  with  the  same 
elevation.  The  cards  will  be  subject  to  inspection  by  coast  defense 
officers  or  other  officers  who  may  be  authorized  to  call  for  them. 

Each  probable  error  card  will  be  prepared  in  triplicate,  one  copy 
being  retained  with  the  battery  records  and  one  each  being  sent 
directly,  without  letter  of  transmittal,  to  the  Chief  of  Coast  Artillery 
and  to  the  coast  defense  officer  at  department  headquarters. 


POINTS  FOR  COAST  ARTILLERISTS  523 

An  officer  taking  command  of  a  battery  should  be  materially 
assisted  by  these  cards,  which  will  indicate  the  accuracy  of  fire  of  the 
guns  of  his  battery  as  mounted  and  with  ammunition  used  from  year 
to  year.  He  can  also,  by  a  proper  combination  of  the  several  results, 
draw  conclusions  as  to  the  mean  results  to  be  expected  from  his  battery 
by  the  following  process: 

It  is  desirable,  of  course,  to  find  the  probable  error  at  each  range 
at  which  firing  takes  place  and  thus  acquire  data  for  a  curve  of  errors 
as  a  function  of  the  range.  It  is  thought  best,  to  begin  with,  to  select 
4,000,  6,000,  and  8,000  yards  as  the  points  to  determine  the  curve 
and  to  reduce  probable  errors  to  these  ranges  as  follows : 

Superimpose  the  centers  of  impacts  of  all  groups  of  shots  fired  at 
odd  times  and  at  different  ranges  between  3,000  and  5,000  yards  at  a 
point  having  a  mid-range  of  4,000  yards;  all  groups  between  5,000 
yards  and  7,000  yards  at  6,000  yards;  all  groups  from  7,000  yards  to 
9,000  yards  at  8,000  yards. 

This  can  be  done  in  the  following  manner: 

Say,  for  instance,  we  have  six  groups  of  shots  between  5,000  and 
7,000  yards,  each  group  fired  at  a  different  range.  Superimpose  the 
centers  of  impacts  of  all  groups  at  a  mid-range  of  6,000  yards,  and  correct 
the  dispersion  of  each  shot  of  each  group  by  finding  the  equivalent 
of  the  actual  dispersion  in  yards,  in  velocity,  and  in  turn  determine 
the  dispersion  at  6,000  yards  which  this  variation  in  velocity  would 
cause.  In  this  way  each  shot  of  each  group  will  be  reduced  to  the 
dispersion  it  should  have  at  6,000  yards.  In  other  words,  the  errors 
from  center  of  impact  of  a  group  of  shots  at  any  range  between  5,000 
yards  and  7,000  yards  will  be  reduced  to  what  they  would  be  at  6,000 
yards  through  velocity.  Having  treated  all  groups  in  this  manner, 
then  the  probable  error  will  be  determined  from  the  total  number  of 
shots  fired  between  5,000  and  7,000  yards  as  if  they  all  belonged  to 
one  group.  In  this  plan  we  assume  that  velocity  variation  is  the 
principal  source  of  error.  This  contemplates  careful  adjustments 
and  preparation  of  material. 

Knowing  what  is  the  best  that  his  guns,  as  mounted  and  with 
ammunition  used  in  practice,  will  do,  the  battery  commander  will 
then  be  able  to  correct  for  observed  errors  with  intelligence,  and  can 
compare  the  accuracy  of  practice  which  he  has  obtained  with  the 
accuracy  of  fire  obtainable  from  his  guns.  Now,  the  probable  error 
of.  any  gun  which  is  obtained  as  indicated  above  is  defined  as  such 
that  just  half  the  shots  fired  will  in  the  long  run  have  an  error  equal  to 
or  less  than  this  probable  error.  The  mean  error  multiplied  by  0.845 


524  THE  SERVICE   OF  COAST  ARTILLERY 

is  the  probable  error.  The  total  width  of  the  50  per  cent,  zone,  which 
is  compared  to  the  target  zone  to  determine  expectation  of  hits,  is 
twice  the  probable  error  or  1.69  times  the  mean  error.  Ballistics, 
Part  I,  by  Captain  Alston  Hamilton,  will  indicate  method  of  deter- 
mining expectation  of  hits. 

It  is  desired  in  practice  to  place  the  center  of  impact  of  a  group 
of  shots  in  the  center  of  the  target  zone.  Therefore,  in  comparing 
the  50  per  cent,  zone  with  the  target  zone  to  determine  expectation 
of  hits,  it  should  be  considered  that  the  point  aimed  at  is  one-fourth 
the  width  of  the  danger  space  beyond  the  water  line  of  the  target. 
This  is  necessary  because  with  the  present  target  the  target  zone  is 
made  up  of  the  danger  space  beyond  the  target  and  one-half  the 
danger  space  short  of  the  target. 

Calibration. — Calibration  has  been  conducted  from  various  batteries 
from  time  to  time.  It  is  the  intention  to  continue  this  firing  as  funds 
will  allow,  the  batteries  in  service  being  calibrated  first.  Full  advan- 
tage should  be  taken  of  the  information  obtained  from  calibration 
firing.  The  purpose  of  this  firing  is  to  enable  such  adjustment  of  the 
range  scales  of  the  guns  of  a  battery  that  all  guns  when  set  at  the  same 
range  reading  will  attain  the  same  range.  When  mean  errors  from 
calibration  firing  have  been  comparatively  small  and  calibration 
data  reliable,  elevation  scales  of  the  guns  of  a  battery  should  be  adjusted 
to  correct  for  differences  in  ranging  of  the  guns. 

In  adjusting  the  scales  of  guns  as  a  result  of  calibration  firing,  a 
gun  of  the  battery  should  be  taken  as  the  standard  gun,  and  all  guns 
should  be  adjusted  to  this  one.  The  gun  first  selected  as  a  standard 
will  always  be  the  standard  gun  of  the  battery.  It  is  desirable,  in  the 
first  adjustment,  that  the  standard  gun  should  be  the  one  whose 
center  of  impact  is  nearest  the  target,  and  that  its  range  scale  be 
not  shifted.  The  range  scales  of  the  remaining  guns  of  a  battery 
should  be  adjusted  so  that  these  guns  when  set  with  the  same  range 
scale  reading  as  the  standard  gun  will  attain  the  same  range  as  that 
gun. 

Complete  record  of  data  obtained  in  calibration  firing  and  adjust- 
ments made  as  a  result  of  this  firing  will  be  kept  in  battery  emplacement 
books,  in  order  that  the  battery  commander  may  have  information 
as  to  differences  in  the  shooting  of  guns  and  the  setting  of  indices  to 
secure  uniformity  in  ranging  of  the  guns  of  the  battery. 

The  method  outlined  above  appears  to  be  the  best  from  a  con- 
sideration of  the  information  at  present  available.  If  as  a  result  of 
calibration  firing  in  the  future  a  better  method  is  determined  upon, 


POINTS  FOR  COAST  ARTILLERISTS  525 

proper  instructions  will  be  furnished  to  all  concerned.  Battery  com- 
manders having  suggestions  to  make  with  reference  to  the  method 
of  calibrating  guns  should  submit  them  in  brief,  concise  form,  with 
reports  of  calibration  firing  to  the  Chief  of  Coast  Artillery. 

After  the  calibration  adjustment  is  made,  then  the  center  of  impact 
of  a  group  of  shots  from  the  battery  may  be  adjusted  to  the  center 
of  the  target  zone,  for  any  practice,  by  means  of  trial  shots  from  any 
gun  of  the  battery. 

There  is  given  below  extract  from  the  proceedings  of  the  board 
which  conducted  calibration  firing  in  1908.  This  firing  was  very  care- 
fully conducted.  It  is  thought  the  report  will  be  of  interest  to  the 
service  and  useful  to  officers  who  have  not  had  experience  in  calibration 
firing.  This  was  the  most  complete  report  of  calibration  firing  sub- 
mitted in  1908. 

The  arrangements  for  and  details  followed  in  the  conduct  of  the 
firing  were"  as  follows: 

The  Station. — A  lighthouse  5,950  yards  from  the  battery  was  used 
as  an  observing  station. 

A  wooden  platform  was  constructed  on  the  lower  braces  of  the 
tower  and  the  range  rakes  mounted  on  the  rail  and  securely  fixed  in 
position  with  the  middle  point,  reference  number  50,  on  the  target. 
The  azimuth  instruments  and  the  camera  were  mounted  on  the  lower 
platform  of  the  lighthouse;  thus  a  solid  platform  was  obtained,  so 
that  the  movements  around  the  instruments  did  not  disturb  their 
adj  ustment. 

Local  conditions  made  it  necessary  to  locate  the  target  400  yards 
from  the  station  instead  of  200  yards,  as  called  for  in  the  instruc- 
tions. 

The  Target. — The  target,  a  standard  pyramidal  target,  was  anchored 
in  position  by  four  500-pound  mine  anchors.  .  .  . 

At  the  time  the  target  was  anchored  it  was  found  impracticable 
to  lay  off  the  distance  of  400  yards,  owing  to  the  fact  that  a  strong 
wind  was  blowing  with  the  tide  coming  in.  The  target  was  anchored 
accurately  for  range  as  determined  by  an  azimuth  instrument  mounted 
on  the  station;  the  distance  by  computation  was  found  to  be  525  yards. 
Observations  made  daily  on  the  target  showed  no  material  movement 
of  the  target  in  range  or  direction. 

Range  Rakes. — New  range  rakes  were  made,  the  points  being 
placed  one-half  inch  apart,  the  value  of  each  point  being  6  yards.  The 
crosspiece  was  made  so  that  it  could  be  adjusted  for  various  distances 
from  observer  to  target.  Reference  numbers  stamped  on  the  rakes 


526  THE   SERVICE   OF  COAST  ARTILLERY 

were  used  to  avoid  confusion,  the  numbers  increasing  from  0  on  the  left 
to  100  on  the  right. 

The  crossarms  were  adjusted  by  a  member  of  the  board  just  before 
the  firing  and  the  range  rakes  bolted  in  position  with  the  meridian 
line  on  the  target.  The  rear  sight  was  43.75  inches  from  the  cross- 
arm,  making  each  point  6  yards.  The  range  observations  were  very 
satisfactory.  The  officers  charged  with  the  work  were  interested,  and 
the  results  demonstrated  that  the  range  rake  is  satisfactory  when  used 
in  an  intelligent  manner.  The  azimuth  instrument  observations  were 
used  as  a  check  on  the  range  rakes,  and  as  such  gave  very  satisfactory 
results.  It  is  believed,  however,  that  the  longer  time  taken  to  turn 
an  azimuth  instrument  on  to  the  splash  gives  the  splash  time  to  spread 
out,  thus  causing  greater  variations  in  separate  readings.  The  value 
of  having  at  least  one  azimuth  instrument  was  demonstrated,  how- 
ever, on  the  first  shot,  which  struck  546  yards  short;  that  is  246  yards 
off  the  range  rakes.  This  splash  was  caught  by  both  azimuth  instru- 
ments. 

The  board  procured  a  Panorama  Kodak  No.  1,  Eastman  Kodak 
Company,  from  the  War  College  for  the  purpose  of  observing  the  fall 
of  the  shots. 

An  observer  at  the  lighthouse  caught  every  shot. 

A  table  about  4  feet  high  was  lashed  to  the  rail  of  the  lower  balcony 
of  the  lighthouse  and  the  camera  was  leveled  on  this  and  the  central 
position  of  the  lens  was  accurately  directed  on  the  target  so  that  the 
latter  would  appear  in  the  same  position  on  each  negative.  The 
camera  was  then  fixed  in  this  position. 

If  there  were  any  imperfections  in  the  camera  lens,  this  arrangement 
insured  that  the  fall  of  the  shots  would  be  measured  under  identical 
positions  of  the  lens,  and  the  comparative  values  of  the  overs  and 
shorts  would  not  be  affected. 

The  observation  by  range  rakes,  azimuth  instrument,  and  camera 
are  tabulated  on  opposite  page,  and  columns  1,  2,  and  3  give  compara- 
tive results  of  the  three  independent  methods. 

The  differences  are  tabulated  in  columns  6  and  7. 

It  will  be  seen  that  the  maximum  difference  is  but  8.67  yards. 

Column  5  gives  the  width  of  splash,  as  shown  by  the  camera,  the 
average  width  being  about  26  yards. 


POINTS  FOR  COAST  ARTILLERISTS 


527 


[All  measurements  are  reduced  to  yards.] 


No. 

Range 
Rakes. 

Azimuth 

Instru- 
ment. 

Camera, 
Inside  of 

Splash. 

Camera 
Outside 
of  Splash. 

Width  of 
Splash. 

Difference, 
Azimuth 
Instrument 
and  Range 
Rake. 

Difference  , 
Camera 
and  Range 
Rake. 

1 

Off  rk. 

546.80 

483.33 

503.33 

.20.00 

2 

114.00 

112.50 

116.67 

143.33 

26.66 

1.50 

2.67 

3 

168.00 

164.08 

166.67 

196.67 

30.00 

3.92 

1.33 

4 

168  .  00 

167.16 

176.67 

200.00 

22.33 

0.84 

8.67 

5 

291.60 

290.56 

290  .  00 

320.00 

30.00 

1.04 

1.60 

6 

168  .  00 

171.84 

173.00 

196.67 

23.67 

3.84 

5.00 

7 

102.00 

101.56 

103  .  33 

126.00 

22  .  34 

0.44 

1.33 

8 

114.00 

111.00 

106.67 

143.33 

36  .  60 

3.00 

7.33 

9 

84.00 

82.76 

83.33 

108.33 

25.00 

1.24 

0.67 

10 

192.00 

193.78 

200.00 

223  .  00 

23.00 

1.78 

8.00 

11 

150.00 

148.36 

146.67 

176.67 

30.00 

1.64 

3.33 

12 

126.00 

128.08 

121.67 

150.00 

28.33 

2.08 

4.33 

13 

192  .  00 

187.05 

200.00 

216.00 

16.00 

4.95 

8.00 

14 

129.60 

128.08 

133.33 

156.67 

23.34 

1.52 

3.73 

15 

225.60 

220.28 

220.00 

256.67 

36  .  67 

.')  .  32 

5.60 

16 

156.00 

159.36 

163.33 

190.67 

27  .  34 

3.36 

7.33 

17 

78.00 

71.56 

76.67 

100.00 

23.33 

6.44 

1.33 

18 

144.00 

140.56 

150.00 

173.33 

23.33 

3.44 

6.00 

Close  agreement  of  the  range  rakes  and  azimuth  instrument  with 
the  photographic  record  shows  excellent  judgment  and  uniform  care- 
fulness on  the  part  of  the  observers. 

From  the  well-known  construction  of  the  panoramic  camera  and 
its  action,  it  is  readily  seen  that  these  negatives  give  the  exact  relative 
locations  of  target  and  splash. 

The  range  rake  and  azimuth  instrument  observers  cannot  avoid 
taking  varying  parts  of  the  successive  splashes,  and  so  may  make 
errors  .as  great  as  20  yards. 

The  camera  record  can  be  measured  at  leisure  and  checked  as  often 
as  may  be  desired. 

The  range-rake  observations  were  taken  as  the  official  records. 

Powder. — The  powder  supplied  for  this  firing  was  Nitro  Gel.  Inter- 
national, Lot.  9,  1907.  V.  2,250  f.  s.,  P.  36,500,  W.  257,  Proj.  1046. 

Owing  to  the  damp  condition  of  the  magazine  this  powder  had  been 
stored  in  a  powder-storage  magazine,  from  the  date  of  its  receipt,  April 
15,  1908,  until  it  was  brought  to  the  fort,  in  June,  1908,  and  placed  in 
the  submarine  mine  storeroom,  where  it  was  served  to  the  guns  as 
needed  in  the  firing. 


528 


THE   SERVICE    OF   COAST   ARTILLERY 


This  powder  gave  very  satisfactory  results  as  to  uniformity,  but 
the  probable  V.  appears  to  have  been  only  2,150  f.  s.,  while  the 
maximum  pressure  recorded  was  only  32,377  pounds.  It  is  believed, 
however,  that  the  pressure  was  higher  than  this. 

Projectiles. — The  projectiles  supplied  -for  this  firing  were  those 
having  the  old-style  cap,  i.e.,  caps  longer  and  of  greater  diameter  than 
the  later  ones. 

Owing  to  age  and  frequent  handling  the  rotating  bands  were  more 
or  less  deformed. 

The  maximum  variation  in  seating  the  projectile  was  0.228  inch 
on  No.  1  gun  and  0.3  inch  on  No.  2  gun.  This  variation  was  too  great 
and  was  due  to  the  use  of  untrained  men  for  the  service  of  the 
piece. 

Crusher  Guages. — Four  crusher  gauges  were  supplied ;  these  were 
handled  by  an  ordnance  machinist  detailed  for  that  purpose  and 
supervised  by  an  officer,  the  results  being  examined  and  checked  by 
a  member  of  the  board.  Cylinders  compressed  to  32,000  pounds  were 
used  for  the  first  shot,  but  as  the  pressure  of  only  32,377  pounds  was 
recorded,  cylinders  compressed  to  28,000  pounds  were  used  for  the 
remaining  shots.  Even  with  these  no  compression  was  recorded  on 
the  seventh,  ninth,  and  tenth  shots.  These  records  are  not  considered 
reliable;  it  is  believed  that  the  pressures  were  higher  and  more 
uniform. 

Density  of  Loading. — The  density  of  loading  varied  to  some 
extent. 

Results  and  Records. — Plotting  of  shots  from  range  rakes  and 
azimuth  instrument  observations  may  be  briefly  tabulated  as  follows: 


No.  1  GUN— RANGE,  5980  YARDS 


Shot. 

Pressure. 
Pounds. 

Struck  Short. 
Yards. 

First  

32,377 

546 

Second 

31  925 

168 

Third  

28,092 

291  6 

Fourth 

* 

102 

Fifth  

* 

84 

Sixth     .  .      . 

30  035 

150 

Seventh  

29,295,5 

192 

Eighth 

29  046 

225  6 

Ninth  ... 

28092 

78 

Maximum  variation  in  seating  of  projectile,  0.228  inch. 
Maximum  variation  in  distance  to  third  section,  2.144  inches. 


*  Not  recorded. 


POINTS  FOR  COAST  ARTILLERISTS 


529 


No.  2  GUN— RANGE,  5950  YARDS 


Shot. 

Pressure. 
Pounds. 

Struck  Short. 
Yards. 

First                                            

32  356 

114 

Second  

28,092 

168 

Third                               .    . 

29  665 

168 

Fourth  

29,572 

114 

Fifth 

* 

192 

Sixth  

29,757 

126 

Seventh                    ... 

31  330 

129  6 

Eighth  

28,092 

156 

Ninth 

29  017  5 

144 

*  Not  recorded. 

Maximum  variation  in  seating  projectile,  0.3  inch. 
Maximum  variation  in  distance  to  third  section,  1.856  inches. 

Comments  and  Conclusions. — Lateral  dispersion  of  fire  is  known  to 
be  small  for  all  modern  rifled  guns,  as  the  deflections  obtained  in  this 
practice  show.  The  necessary  correction  for  such  dispersion  is  so  easily 
determined  and  so  readily  applied  in  practice  that  it  may  be  omitted 
from  this  report. 

A  careful  study  of  the  results  and  due  consideration  of  the  con- 
ditions and  circumstances  of  the  firing  indicate  to  the  board  the  follow- 
ing conclusions: 

1.  That  whatever  erosion  or  other  imperfection  may  have  existed 
in  the  guns  themselves,  the  effects  of  stich  imperfections  were  of  least 
importance  in  producing  inaccuracy  of  fire  when  compared  with  the 
mount. 

2.  That  the  chief  source  of  inaccuracy  was  the  mount;    it  being 
the  opinion  of  the  board  that  with  each  of  the  carriages  used  the  "  jump " 
of  the  gun  was  an  important  element,  probably  negative  in  value 
and  variable  in  amount. 

3.  That  blending  should  be  required  at  all  times. 

The  board  believes  that  the  method  of  blending,  while  accurate, 
is  not  suitable  to  service  conditions.  The  board,  however,  is  of  the 
opinion  that  all  powder  should  be  blended,  whether  in  practice  or  in 
service.  Under  war  conditions  powders  from  various  sources  will  be 
found  at  every  post,  all  manufactured  under  the  same  specifications 
of  the  Ordnance  Department,  but  varying  slightly  in  velocity,  rate 
of  burning,  etc. 

Velocity  for  Trial  Shots.— Such  velocity  should  be  assumed  for  the 
trial  shots  as  will  bring  these  shots  as  near  as  possible  to  the  target. 


530  THE   SERVICE   OF  COAST   ARTILLERY 

On  account  of  the  fact  that  a  great  many  powders  have  fallen  off  in 
velocity  and  are  considerably  under  the  velocity  tabulated  in  general 
orders,  as  determined  by  tests  of  the  Ordnance  Department,  it  may  be 
necessary  for  battery  commanders  to  base  their  assumption  as  to  the 
muzzle  velocity  of  their  powder  for  trial  shots  on  previous  experience 
obtained  with  this  powder  either  by  themselves  or  others  in  the  service. 
For  this  reason  there  is  available  a  tabulation  showing  the  mean  results 
obtained  with  the  various  lots  of  powder  in  use  throughout  the  service. 

Determination  of  Range  Errors  of  Trial  Shots. —  .  .  .  All  officers 
should  strive  to  eliminate  these  errors  in  the  observation  of  trial  shots. 
The  greatest  care  must  be  exercised  by  range  observers  on  the  tug  in 
observing  splashes,  and  there  should  be  a  thorough  understanding  by 
the  officers  on  the  tug  and  those  on  shore  as  to  the  method  of  signaling 
to  be  used.  Range  rakes  will  be  inspected  by  the  officer  in  charge  of 
range  observers  before  the  practice.  These  rakes  will  be  graduated  in 
mils.  The  tug  will  be  anchored  opposite  to  and  as  nearly  as  possible 
at  right  angles  to  the  line  joining  gun  and  target.  The  position  of 
tug  and  target  immediately  before  and  after  each  shot  will  be  observed 
by  the  position  finders  of  the  battery  firing  and  these  positions  plotted 
on  the  plotting  board  in  order  that  mils  can  be  correctly  converted 
into  yards  when  they  are  signaled  in. 

If  the  first  trial  shot  should  fall  too  great  a  distance  from  the  target 
to  permit  of  its  accurate  observation  by  the  range  party,  the  battery 
commander  should  change  the  elevation,  provided  he  believes  that 
the  error  was  due  to  faulty  assumption  as  to  muzzle  velocity,  so  that 
the  remaining  shots  will  fall  near  the  target.  If  this  is  done  properly 
the  battery  commander  should  then  have  the  benefit  of  at  least  two 
good  trial  shots.  Having  fired  the  trial  shots,  if  these  are  normal  and 
the  errors  are  small,  the  general  practice  is  to  take  the  mean  of  the  errors 
of  these  shots  in  making  corrections  for  velocity  for  record  shots.  If 
one  or  more  shots  are  erratic,  it  may  be  the  erratic  shot  or  shots  should 
be  thrown  out,  although  this  depends  on  the  circumstances.  The 
problem  must  be  solved  on  its  merits  in  each  case  by  the  battery 
commander  and  no  definite  rules  can  be  laid  down.  With  the  present 
target  such  assumption  as  to  velocity  for  record  shots  should  be  made 
as  will  place  the  center  of  impact  one-fourth  the  width  of  the  danger 
space  beyond  the  water  line  of  the  target. 

Adjustment  of  Center  of  Impact. — To  aim  at  a  point  one-fourth  the 
danger  space  proper  beyond  the  target  is  equivalent  to  aiming  at  a  point 
on  the  target  7^  feet  above  the  water  line.  As  the  present  target  is  30 
feet  high  (see  Fig.  90)  and  therefore  the  point  to  be  aimed  at  is  7^  feet 


POINTS  FOR  COAST  ARTILLERISTS 


531 


above  the  water  line,  if  we  make  correction  for  plus  7^  feet  in  the  same 
way  as  the  correction  is  made  for  plus  tide  we  accomplish  the  desired 
result.  It  will  be  seen  that  when  the  trial  shots  are  fired  at  one  range 
and  their  center  of  impact  is  adjusted  for  one-fourth  the  width  of  the 
danger  space  beyond  the  target  for  that  range,  this  fixed  correction 
will  not  be  the  true  one  when  the  record  shots  are  fired  at  different 
ranges.  An  officer  of  the  Coast  Artillery  Corps  has  suggested,  in 
order  that  the  proper  correction  may  be  made  at  all  ranges,  that  a  curve 
be  constructed  on  the  range  chart  for  7J  feet  of  tide.  This  curve 
may  be  put  on  the  range  chart  in  pencil  and  can  be  placed  conveniently 
to  the  left  of  the  travel  scale,  using  the  left  vertical  line  of  travel  scale 
for  the  normal  of  the  curve.  It  should  be  understood  that  this  correc- 


FIG.  90. 

tion  for  placing  the  center  of  impact  in  the  center  of  the  target  zone  is 
in  addition  to  the  other  corrections  now  provided  for  on  the  range  board. 
Observation  of  Fire. — The  question  of  the  observation  of  fire  has 
received  considerable  thought  and  the  policy  in  regard  thereto  was 
outlined  in  a  memorandum  from  the  office  of  the  Chief  of  Coast  Artillery, 
dated  June  1,  1908.  This  memorandum  pointed  to  the  conclusion  that 
corrections  based  on  observation  of  fire  were  inadvisable  in  the  case  of 
batteries  equipped  with  a  separate  position-finding  system,  viz.,  the 
8-inch,  10-inch,  and  12-inch  rifles,  and  the  more  important  6-inch 
batteries,  in  view  of  the  fact  that  observations  of  overs  and  shorts 
have  been  found  to  be  unreliable.  It  was  stated  in  this  memorandum 
as  the  opinion  of  the  Chief  of  Coast  Artillery  that  it  was  not  thought 
advisable  for  battery  commanders  to  apply  corrections  based  on 
observations  of  fire  until  they  had  assured  themselves,  through  the 
observation  of  a  number  of  shots,  that  there  was  a  constant  error  in 
the  ranges  for  which  the  guns  were  laid.  It  is  believed  that  the  number 
of  shots  upon  which  any  correction  is  based  should  be  not  less  than  three. 


532  THE   SERVICE   OF   COAST  ARTILLERY 

Therefore,  if  the  battery  commander  by  observation  determines  the 
fact  that  three  or  more  shots  have  fallen  uniformly  short  or  over,  he 
should  then  make  an  arbitrary  correction  to  cause  the  remaining  shots 
to  fall  in  the  center  of  the  danger  space.  Correction  should  not  be 
made  when  the  fall  of  the  shots  is  within  the  mean  error  as  determined 
by  the  trial  shots.  Observation  of  fire  with  heavy-gun  batteries  is 
the  last  step  in  the  solution  of  the  target-practice  problem.  In  this 
problem  we  must  start  with  the  gun  and  eliminate  all  source  of  error 
there  first.  Having  done  this,  then  if  the  shot  does  riot  strike  the 
target  we  know  that  the  manipulation  of  the  gun  has  been  -faulty; 
that  is,  errors  have  arisen  in  the  range  finding  and  the  proper  applica- 
tion of  the  data  determined  by  the  position-finding  system  to  the  guns. 
We  may  say,  therefore,  that  observation  of  fire  is  a  means  of  correcting 
errors  in  the  position-finding  service  or  the  manipulation  of  the  gun; 
and  to  employ  it  intelligently  we  must  assume  that  the  errors  we  are 
correcting  for  are  constant.  It  will  be  appreciated  that  the  most  difficult 
step  in  observation  of  fire  is  the  correct  determination  of  the  range 
errors.  This  is  practically  impossible  excepting  at  very  short  ranges. 
On  high  sites  observation  of  fire  is  more  feasible;  even  on  these  sites 
the  errors  of  shots  can  be  correctly  estimated  only  at  short  ranges. 
When  errors  can  be  determined  by  observation  any  correction  made 
as  a  result  thereof  will  be  made  by  the  battery  commander  and  not  by 
the  gun  pointers. 

At  a  test  with  3-inch  guns,  it  developed  that  observation  of  fire  was 
unreliable'  except  at  very  short  ranges  for  the  ordinary  height  of  battery. 
Range  errors  short  of  the  target  could  be  fairly  well  estimated,  but 
it  was  practically  impossible  to  estimate  reliably  the  errors  of  the  shots 
that  fell  beyond  the  target.  As  a  result  of  this  test  in  which  a  great 
number  of  rounds  were  fired,  the  following  conclusions  on  the  proper 
method  of  making  corrections  from  observation  of  fire  with  rapid-fire 
batteries  were  arrived  at: 

That  range  corrections  based  on  observation  of  fire  should  be 
made  only  by  the  battery  commander. 

That  deflection  corrections  with  rapid-fire  guns  should  be  made 
by  gun  pointers.  The  training  of  gun  pointers  is,  therefore,  of  great 
importance. 

That  velocity  corrections  as  a  result  of  trial  shots  with  rapid-fire 
guns  may  be  applied  by  shifting  the  range  scale  or  the  pointer,  or  by 
correcting  the  ranges  determined  by  the  range  finder,  before  these 
ranges  are  posted." 


POINTS  FOR  COAST  ARTILLERISTS 


533 


VALUE   IN   YARDS   OF   POINTS   OF   DEFLECTION 

During  subcaliber  and  service  practice,  battery  commanders  should 
record  and  study  deflections.  In  this  connection  the  following  table 
will  be  found  beneficial. 


Hundred  ths  of  degrees  

5 

10 

15 

90 

25 

30 

35 

40 

45 

50 

Minutes 

3 

6 

q 

1? 

15 

18 

91 

94 

97 

30 

Points  

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

RANGES 

VAL 

UE  I 

x  Y 

ARD 

s 

1  000  

1 

2 

3 

4 

5 

6 

7 

8 

q 

10 

2  000          .... 

2 

4 

6 

8 

10 

12 

14 

16 

18 

20 

3  000  

3 

6 

q 

19 

15 

18 

21 

94 

97 

30 

4  000 

3 

6 

9 

12 

15 

18 

21 

24 

27 

30 

5  000     

4 

8 

12 

16 

?0 

94 

28 

39 

36 

40 

6  000 

5 

10 

15 

20 

25 

30 

35 

40 

45 

50 

7  000       

6 

12 

18 

94 

30 

36 

49 

48 

54 

60 

8,000  

7 

14 

21 

98 

35 

49 

49 

56 

63 

70 

9  000 

8 

16 

24 

39 

40 

48 

56 

64 

72 

80 

10,000  

9 

18 

97 

36 

45 

54 

63 

79 

81 

90 

11  000 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

12,000  

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

NOTE. — This  table  is  not  exactly  accurate,  the  value  of  one  point  at  1,000  yards  is  exactly 
0.87426  yards,  but  as  the  error  is  less  than  one  yard  it  may  be  used  safely  for  all  firings  under 
Case  II.  The  value  of  one  point  may  therefore  be  taken  as  .001  of  the  range,  or  equal  to  one  mil. 

All  ballistic  corrections  which  battery  commanders  may  desire  to 
make  should  be  sent  through  the  primary  station.  They  should  see 
that  an  accurate  record  is  kept  of  all  shots  fired. 

In  battle  and  fire-command  drills  after  receiving  the  order  announc- 
ing the  kind  of  fire,  battery  commanders  state  the  kind  of  projectile 
to  be  used,  the  character  of  fire  and  command,  "Commence  firing/' 

At  target  practice  they  see  that  all  reports  are  properly  and  promptly 
transmitted. 

During  drills  men  temporarily  disengaged  should  be  required  to 
remain  silent  and  alert.  No  talking  or  smoking  should  be  permitted 
at  emplacements  or  stations  under  any  circumstances. 

No  person  should  be  allowed  on  the  parapet  during  drill  or  practice. 

Battery  commanders  should  remain  constantly  at  their  proper 
stations  unless  called  away  for  some  urgent  reason,  in  which  event 
they 'leave  word  where  they  can  be  found. 


534  THE   SERVICE   OF  COAST  ARTILLERY 

The  possibility  of  gun  pointers  or  others  being  disabled  should  be 
provided  for  and  their  successors  named  in  advance. 

The  following  are  the  proper  commands  for  battery  commanders: 

To  load  and  fire: 

"No.  1  (or,  No.  2),  With  dummy  pi£>jectile;  Fire  one  shot,  Com- 
meiie  Firing." 

"No.  1  (or,  No.  2),  With  A.  P.  Shot,  Fire  one  shot,  Commence 
Firing." 

"No.   1   (or,  No.  2),  With  dummy  projectile,  Commence  Firing." 

"With  dummy  projectile,  Fire  one  round,  Commence  Firing." 

"With  A.  P.  Shot,  Commence  Firing." 

"With  Subcaliber  ammunition  (or,  C.  I.  Shot,  or,  Dummy  Pro- 
jectile, etc.),  Commence  Firing." 

During  battery  drill  battery  commanders  designate  targets  in  the 
same  manner  as  prescribed  for  fire  commanders. 


EMPLACEMENT   OFFICERS 

Emplacement  officers  should  be  so  familiar  with  the  entire  mechan- 
ism of  guns  and  carriages  as  to  be  able,  if  necessary,  to  take  the  place  of 
any  enlisted  man  in  the  gun  section. 

They  should  be  perfectly  capable  of  making  any  repairs  of  a  minor 
nature  that  may  be  necessary  during  drill  or  action.  They  should 
have  a  practical  working  knowledge  of  breechblocks,  firing  mechanisms, 
the  recoil  system  and  stuffing  boxes,  as  well  as  sights  and  the  various 
equipment  incidental  to  guns  and  mortars. 

No  emplacement  officer  is  capable  of  doing  the  work  which  the 
position  requires  unless  he  has  a  practical  working  knowledge  of  each 
position  on  the  gun. 

Emplacement  officers  should  take  every  opportunity  to  teach 
enlisted  men  the  theory  of  the  work,  that  is,  the  theory  of  pointing 
and  laying  guns;  the  meaning  of  Case  I,  Case  II,  and  Case  III;  as 
well  as  the  part  each  of  them  plays  in  the  logical  chain  of  events  which 
begins  at  the  target,  thence  to  the  primary  and  secondary  stations, 
thence  to  the  guns  and  back  to  the  target  again. 

A  close  study  of  the  illustrations  found  herein  of  the  several  types  of 
guns,  mortars  and  various  equipment  connected  therewith,  will  be 
found  a  great  help  in  their  studies. 

Emplacement  officers  are  responsible  to  the  battery  commander 
that  all  parts  of  the  guns  and  carriages  are  in  perfect  working  'order 


POINTS  FOR  COAST  ARTILLERISTS  .     535 

and  that  all  necessary  adjustments  are  properly  made.  They  are 
responsible  for  safety  during  drill  and  action.  They  should  see  that 
their  men  work  with  calmness  and  speed,  keeping  constantly  in  mind 
that  proper  seating  of  the  projectile,  careful  handling  of  powder,  proper 
locking  of  the  breech,  proper  swabbing  of  the  powder  chamber  after 
each  shot,  are  all  matters  of  vast  importance — each  of  which  takes  prece- 
dence over  speed. 

Emplacement  officers  see  that  the  ammunition  specified  is  used, 
that  the  artillery  discipline  during  drill  or  action  is  constantly  main- 
tained, that  men  disengaged  stand  at  ease,  that  in  moving  from  place 
to  place  the  men  do  so  at  double  time,  and  that  all  orders  are 
instantly  obeyed. 

RANGE   OFFICERS 

Range  officers  should  be  perfectly  capable  of  operating  and  adjusting 
every  instrument  in  the  fire-control  stations.  This  knowledge  should 
be  such  that  in  case  minor  repairs  are  necessary  they  can  make  them. 

Upon  arrival  at  the  station  the  range  officer  should  see  that  each 
man  examines  and  properly  adjusts  the  instrument  to  which  he  is 
assigned  and  that  the  proper  reports  are  made  to  the  Plotter.  The 
reports,  when  no  defects  are  found,  are  as  follows:  "  B  Prime,  In  Order." 
"B  Second,  In  Order."  "Deflection  Board,  In  Order."  "Range 
Board,  In  Order."  "Telautograph,  In  Order."  "F.  C.  Intelligence, 
In  Order."  "  B.  C.  Line,  In  Order."  "  Gun  Line,  In  Order."  "  Secondary 
Intelligence,  In  Order." 

The  Plotter,  after  having  received  the  above  reports  (or  reports 
of  any  repairs  necessary),  and  after  making  the  adjustments  of  the 
equipment  to  which  he  is  assigned,  reports  to  the  range  officer:  "Sir, 
Plotting  Room,  In  Order"  (or  reports  such  defects  as  cannot  be  readily 
corrected) . 

The  Observer,  after  satisfying  himself  that  the  observing  room 
equipment  is  in  order  and  that  the  position-finding  instrument  is  in 
proper  adjustment,  reports  to  the  range  officer:  "Sir,  Observing  Room, 
In  Order."  . 

After  the  range  officer  has  satisfied  himself  by  personal  inspection 
that  everything  is  in  readiness,  including  Secondary  Station,  he  reports 
to  the  battery  commander:  "Sir,  Fire  Control  Stations,  In  Order" 
(or  reports  any  defects  that  cannot  be  readily  corrected). 

Upon  orders  being  received  from  the  battery  commander  designating 
a  target,  the  range  officer  commands: 


536  THE  SERVICE   OF  COAST  ARTILLERY 

"Target  (repeating  the  battery  commander's  description  verbatim; 
and  adding  any  other  information  that  may  facilitate  identification)." 

After  the  target  has  been  identified  by  the  primary  and  secondary 
observers  and  the  gun  pointer  (or,  if  vertical  base  system  is  used,  by  the 
primary  observer  and  gun  pointer) ,  the  range  officer  commands : 

"Horizontal  (or,  Vertical)  Base,  Track." 

He  then  reports  to  the  battery  commander  over  the  B.  C.  line: 

"Target." 

Upon  orders  being  received  from  the  battery  commander  to  change 
target,  etc.,  the  range  officer  commands: 

"Cease  Tracking.  Change  Target.  Target  (repeating  description, 
etc.)." 

At  the  end  of  the  drill  or  exercise,  the  range  officer  commands: 

"Close  Station." 

In  the  case  of  battle  or  fire-command  drill  or  action,  he  transmits 
the  following  message  from  the  battery  commander  to  the  fire  com- 
mander: 

"Dix,  In  Order."  (Or,  reports  repairs  which  the  battery  com- 
mander deems  necessary.) 

When  a  target  is  assigned  by  the  fire  commander  and  after  it  has 
been  properly  identified,  the  range  officer  sends  the  following  message 
to  the  fire  commander: 

"Dix,  Target." 

The  range  officer  receives  directly  from  the  fire  commander, 
and  executes,  orders  as  to  the  assignment  of  targets;  and  when  direct 
communication  between  the  fire  commander  and  the  battery  com- 
mander is  impracticable,  he  receives  directly,  and  executes,  other 
orders  pertaining  to  the  fire  action  of  the  battery.  He  is  responsible, 
however,  for  the  prompt  and  accurate  transmission  to  the  battery 
commander  of  all  orders  received  by  him  directly  from  the  fire  com- 
mander. 

TUG   OFFICER   AND   TUG   OBSERVER 

An  experienced  officer  not  belonging  to  the  company  firing,  prefer- 
ably a  district  staff  officer,  is  in  charge  of  the  tug  during  service 
practice. 

The  tug  officer  determines  the  overs  and  shorts  for  all  shots  except 
the  record  practice  of  guns  below  4.7  inches  in  caliber.  He  is  assisted 
by  an  officer  or  a  non-commissioned  officer  equipped  with  a  camera 
or  a  range  rake.  (For  description,  see  DEFINITIONS.)  For  trial  shots 


POINTS  FOR  COAST  ARTILLERISTS  537 

both  observers  obtain  the  overs  and  shorts  in  mils.  For  record  shots 
of  mortar  batteries  and  of  gun  batteries  above  4-inch  the  assistant 
observer  uses  the  camera,  if  available;  otherwise  the  range  rake. 
When  both  observers  are  using  range  rakes,  the  results  of  the  observa- 
tions on  the  tug  shall  not  be  called  or  spoken  aloud,  but  shall  be  recorded 
without  comment  by  the  observer  as  soon  as  made.  The  observer  shall 
sight  on  the  edge  of  the  splash  nearest  the  gun.  The  average  of  the 
deviations  determined  by  the  observers  when  both  are  using  range 
rakes  shall  be  recorded  as  the  deviation  normal  to  the  line  joining  the 
tug  and  target.  When  record  is  obtained  with  the  camera  the  range- 
rake  observation  shall  be  discarded  and,  under  direction  of  the  fire 
commander,  the  camera  record  reduced  to  yards.  The  records  are 
submitted  to  the  fire  commander  on  the  proper  form,  who  may  discard 
the  deviations  reported  by  any  observer  upon  satisfactory  representa- 
tion by  the  officer  in  charge  of  the  range  party  on  the  tug  that  the 
observation  was  probably  erroneous.  The  points  of  attachment  of  the 
towline  to  the  targets  and  the  point  of  the  towline  at  the  position 
occupied  by  the  observers  on  the  tug  shall  be  marked  by  tying  cloth 
around  the  towline  or  by  other  suitable  means.  Immediately  after 
the  practice  and  while  still  wet  the  towline  shall  be  detached  from  the 
tug  and  targets,  stretched,  and  measured  accurately  between  the  points 
marked,  under  the  supervision  of  the  officer  in  charge  of  the  tug,  and 
the  result  of  this  measurement  shall  be  entered  on  the  proper  form  as 
the  length  of  the  towline.  No  allowance  shall  be  made  for  sag. 

Tug  officers  are  responsible  that  the  following  material  is  on  the 
tug  whenever  it  goes  out  for  target  practice. 

One  copy  of  current  Coast  Artillery  Instruction  Memorandum; 
one  copy  of  Tug  Service;  six  forms  No.  823;  one  red  streamer;  three 
range  rakes;  600  yards  of  towing  line;  300  yards  of  anchor  rope; 
3  buoys;  all  the  target  anchors  available;  paint  pot  and  brush,  for 
marking  out  subcaliber  hits;  two  pairs  of  field  glasses;  one  army 
signal  code  card;  two  red  wig-wag  flags;  one  measuring  tape;  two 
cameras;  one  memorandum  pad. 

Each  launch  should  be  equipped  with  a  red  streamer,  a  red  signal 
flag,  and  a  copy  of  Tug  Service. 

Each  tug  should  be  equipped  with  wireless  telegraph  apparatus  in 
order  to  communicate  with  the  officer  in  charge  of  the  firing  as  well 
as  to  promptly  inform  the  battery  commander  of  the  range  deflections 
of  trial  shots. 

Tug  officers  are  responsible  for  the  efficiency  of  the  tug  detail, 
which  should  consist  of  the  necessary  number  of  men  to  handle  targets, 


538  THE   SERVICE   OF   COAST   ARTILLERY 

to  watch  shore  signals,  to  read  or  send  wig-wag  signals,  and  to  use  the 
cameras. 

The  actual  maneuvering  of  targets  from  tug  will  be  under  the 
supervision  of  the  master  of  the  tug. 

All  personnel  detailed  for  tug  service  should  provide  themselves  'with 
lunches. 

Each  fixed  target  should  be  anchored  with  two  heavy  anchors  and 
buoyed;  a  rectangular  target  always  broadside  to  the  battery. 

As  far  as  practicable  targets  should  be  planted  the  day  before  firing. 

A  fixed  target  should,  whenever  practicable,  be  left  down  as  a  marker 
on  the  selected  course  for  practice  at  a  moving  target. 

In  anchoring  the  tug  to  observe  splashes  or  hits  for  fixed  target, 
always  take  position  to  left  of  target  (as  viewed  from  the  battery)  on 
a  line  perpendicular  to  line  of  fire,  about  200  yards  when  rectangular 
target  is  used,  300  yards  for  service  gun  practice,  and  500  yards  for 
mortar  practice  (subcaliber  and  service).  Always  anchor  tug  for  trial 
shots.  For  description  of  targets,  see  Pyramidal  and  Material  Targets, 
in  the  DEFINITIONS. 

The  nearest  towed  target,  to  the  tug,  for  gun  fire  will  always  be 
200  yards,  and  for  mortars  500  yards. 

Towline  will  always  be  stretched  and  measured  wet,  immediately 
after  returning  from  practice  under  the  direct  supervision  of  the  senior 
tug  observer;  the  measured  length  being  noted  on  report. 

The  senior  tug  officer  will  report  to  the  Umpire  and  Fire  Com- 
mander, before  going  out,  for  written  instructions  and  a  harbor  chart 
with  positions  of  targets,  courses,  etc.,  indicated  thereon.  This  chart, 
with  report,  will  be  returned  to  the  Umpire  immediately  after  the 
return  of  the  tug  party  to  post. 

The  charted  course  for  a  moving  target  may  often  serve  as  a  general 
guide  only,  or  unexpected  developments  may  change  plans  ashore. 
Consequently  it  may  often  happen  that  the  tug  will  have  to  be  run  on 
course  by  signals  from  the  signal  station  ashore.  A  constant  lookout 
will  be  maintained  for  such  signals,  and  they  must  be  promptly  and 
accurately  obeyed. 

Before  leaving  for  day's  work,  the  senior  tug  officer  will  set  his 
watch  on  post  time. 

SHORE   TUG   SIGNALS 

A  flag  will  be  designated  on  shore  for  the  purpose  of  displaying  the 
firing  signal,  and  will  be  used  for  no  other  purpose.  The  firing  signal 


POINTS  FOR  COAST  ARTILLERISTS 


539 


staff  will  be  located  in  the  immediate  vicinity  of  the  battery  firing, 
preferably  near  the  center. 

A  long  red  streamer  will  be  displayed  from  the  firing  signal  staff 
and  one  on  the  tug.  In  no  case  will  firing  be  permitted  unless  the  red 
streamer  is  displayed  both  ashore  and  afloat.  As  a  rule,  the  first 
signal  will  be  displayed  on  shore,  the  tug  displaying  its  streamer  as 
soon  as  the  range  is  clear.  In  case  of  danger  to  tug  or  to  any  other 
boats  near  the  field  of  fire,  the  tug  will  lower  streamer,  shore  station 


Anchor  target. 
5. 


Take  up  anchor.  ' 
6. 


Proceed  to  execute  what 
is  prescribed  next. 

7 


Indicate  Score. 
8. 


Halt  and  await 
further  orders. 

9. 


Take  course  for  practice 
at  moving  target. 

/O. 


To  your  right. 


To  your  left. 
IS. 


\ 


Turn  about. 


Increase  range.  Decrease  range. 

FIG.  91. 


Come  in,  practice  ended. 


immediately  responding.  The  whistle  signal  of  "D"  222  will  also 
be  given  from  the  tug. 

During  subcaliber  mortar  firing,  on  account  of  the  difficulty  of 
catching  mortar  splashes,  the  red  streamer  will  be  run  down  and  up 
several  times  as  a  warning  immediately  after  each  shot  is  fired. 

The  " Maneuver"  signal  staff  will  be  located  in  the  immediate 
vicinity  of  the  Fire  Commander's  station. 

The    accompanying    diagram     (Fig.    91)    represents     the    various 


540  THE  SERVICE   OF  COAST  ARTILLERY 

maneuver  signals  as  they  would  appear  when  viewed  from  the  tug. 
Owing  to  their  lightness  and  uniformity  of  dimensions  four  ordinary 
megaphones  may  be  used,  when  available,  in  forming  signals  until 
cones  or  disks  are  supplied. 


REMARKS  ON  MANEUVER  AND  SOUND  SIGNALS 

The  tug  should  drop  target  anchors  as  promptly  as  possible  after 
Signal  No.  1  is  shown  on  shore.  If  the  tug  is  not  fitted  with  appliances 
for  tripping  anchors  at  word  of  command  drop  a  marking  buoy  at  once. 

(a)  The  tug  will  acknowledge  all  maneuver  signals  by  one  long 
blast  followed  by  two  toots  in  quick  succession. 

(6)  The  shore  signal  will  be  lowered  as  soon  as  the  tug  acknowledges. 
If  signal  is  One  that  puts  tug  in  motion,  it  will  continue  in  the  direction 
indicated  until  some  other  signal  is  displayed  on  shore. 

(c)  Signal  up  and  down  several  times,  means  go  slow,  to  be  acknowl- 
edged by  the  tug  as  soon  as  made  out,  after  original  acknowledgment. 

(d)  Signal  No.  3. — This  means  proceed  to  next  step  indicated  in 
tug  officer's  orders. 

(e)  Signal  No.  4. — The  following  designations  are  used: 

Hit.     "H"  [122]  1  toot,  2  toots,  2  toots. 

Over.     "O"  [21J  2  toots,  1  toot. 

Short.     "S"  [212]  2  toots,  1  toot,  2  toots. 

To  indicate  the  number  of  hits  at  subcaliber  gun  practice;  acknowl- 
edge Signal  No.  4.  After  marking,  Signal  "  H,"  considerable  pause, 
followed  by  one  toot  for  each  hit.  If  no  hits,  signal  "  H"  only. 

To  indicate  the  result  of  a  trial  shot  at  service  gun  practice,  and 
mortar  practice  (subcaliber  and  service)  acknowledge  Signal  No.  4, 
long  pause,  toot  "S"  or  "0"  as  the  case  may  be,  considerable  pause 
followed  by  one  toot  for  each  division  of  the  range  rake.  If  there  is 
no  deviation  signal  "O"  only.  In  the  case  of  shot  off  the  rake,  after 
"S"  or  "  O"  give  one  long  blast,  marked  pause,  and  one  toot  fcr 
every  five  divisions  of  estimated  deviation. 

Make  a  distinct  pause  between  toots  in  a  series  indicating  hits  or  mils 
so  that  successive  puffs  of  steam  can  be  clearly  distinguished. 

(/)  Halt  (No.  5)  repeated  means  a  probable  intermission  or  delay 
of  half  an  hour  for  each  repetition. 

(g)  Signals  Nos.  7  and  8. — If  at  a  halt  move  in  direction  perpen- 
dicular to  line  joining  tug  and  Fire  Commander's  station,  rights  or 


POINTS  FOR   COAST   ARTILLERISTS  541 

lefts  being  determined  as  tug  observer  faces  this  station.  If  in  motion 
bear  off  in  direction  indicated  (as  tug  observer  faces  bow)  by  one  point 
(about  11  degrees).  To  make  a  considerable  change  in  direction 
repeat  necessary  number  of  times. 

(h)  Signal  No.  9. — Tug  will  make  a  turn  of  180  degrees  to  right. 
If  once  repeated  turn  to  left.  (In  either  case,  as  observer  faces  bow.) 

(i)  Signals  Nos.  10  and  11. — Move  directly  away  from  or  towards 
Fire  Commander's  station  as  the  case  may  be. 


SOUND   SIGNALS 

Tug  will  use  following  conventional  sound  signals: 

" D"  222  (2  toots,  2  toots,  2  toots),  Danger  to  tug  or  to  boats  in  the 
vicinity. 

"W"  1121  (1  toot,  1  toot,  2  toots,  1  toot),  Something  wrong  on 
board,  am  having  trouble. 

"K"  2121  (2  toots,  1  toot,  2  toots,  1  toot),  All  right  now,  am  ready 
to  resume  work. 

"X"  2122  (2  toots,  1  toot,  2  toots,  2  toots),  Have  executed  what 
was  ordered  last  (used  generally  after  a  movement  requiring  some 
time  to  execute,  has  been  completed  as  directed  by  Signal  No.  3). 


WIG-WAG   SIGNALS 

(a)  The  shore  flagman  will  be  posted  near  the    maneuver   signal 
staff. 

(b)  The  tug's  call  letter  is  "T".     The  shore  station's  call  letter  is 
"F." 

(c)  The  tug  will  never  be  called  unless  Signal  No.  5  is  first  displayed. 
If  tug  wishes  to  call  shore,  the  tug  will  always  do  so  from  a  halt.     In 
the  latter  case,  in  addition  to  the  usual  wig-wag  call,  the  tug  will  toot 
"F"  (2221)  2  toots,  2  toots,  2  toots,  1  toot, 

(d)  Tug  will   acknowledge  wig-wag  call  in  the   same   manner   as 
prescribed  in  the  case  of  maneuver  signals,  this  in  addition  to  the  flag- 
man's acknowledgment. 

(e)  The  tug  flagman  should  be  posted  well  up  on  the  upper  deck 
with  the  sky  as  a  background,  and  a  red  flag  should  be  used. 

Whenever  practicable,  the  shore  flagman,  also,  should  use  a  sky 
background. 


542  THE   SERVICE   OF  COAST  ARTILLERY 


NIGHT   SIGNALS 

For  maneuvering  at  night,  the  Battle  Commander's  searchlight  is 
used  to  indicate  the  number  of  disks  or  cones  used  for  each  of  the 
maneuver  signals. 

The  beam  is  first  directed  over  the  smokestack  of  the  tug  and 
then  swung  in  arcs  of  about  30  degrees  to  the  right  or  left,  as  seen  from 
the  tug.  When  both  right  and  left  are  required,  the  right  arcs  are 
made  first.  For  example,  maneuver  signal  No.  3  would  be  one  swing 
to  the  tug  observer's  right  and  three  to  his  left;  signal  No.  6,  would 
be  two  swings  to  tug  observer's  right  and  two  to  his  left. 


WIRELESS   COMMUNICATION 

When  wireless  communication  is  used,  the  maneuver  signals 
are  communicated  by  number,  prefixed  by  the  letter  M.  For  example, 
the  maneuver  signal  indicating  "Take  up  anchor,"  would  be  sent  "  M2." 


OBSERVERS 

Observers  are  trained  out  of  drill  hours,  to  observe  fixed  objects,  the 
distance  of  which  are  accurately  known,  until  they  can  quickly  deter- 
mine ranges  with  accuracy.  Officers  in  immediate  command  of 
observers  test  their  proficiency  in  the  following  manner:  After  the 
observer  has  properly  adjusted  the  instrument  (as  explained  in 
Chapter  VII),  the  range  and  azimuth  scales  are  covered. 

The  officer  then  indicates  the  object  (the  range  and  azimuth  of 
which  is  accurately  known),  and  commands:  "Take,"  at  the  same 
time  starting  his  stop-watch.  As  soon  as  the  observer  has  completed 
the  observation,  he  reports,  "  Now." 

The  officer  then  stops  the  watch  and  personally  reads  the  range 
and  azimuth  from  the  scales  of  the  instrument,  making  a  record  of  the 
readings  as  well  as  the  time  between  "take"  and  "now."  Several 
points  are  located  in  a  like  manner  and  the  operation  repeated  until 
three  observations  have  been  made  on  each  point. 

Observers  should  carefully  study  the  methods  of  water-lining, 
(See  Depression  Position  Finder,  Chapter  VII).  They  should  con- 
tinually follow  the  target,  keeping  the  vertical  cross-wire  a  shade 
in  front  of  the  point  upon  which  it  is  desired  to  have  the  instrument 


POINTS  FOR  COAST   ARTILLERISTS  543 

point  at  the  third  stroke  of  the  time-interval  bell,  so  that  when  the 
traversing  of  the  instrument  is  stopped  on  the  third  stroke  of  the  bell 
the  wire  will  be  accurately  on  the  center  of  the  target,  or  point  upon 
which  it  is  desired  to  aim. 

Observers  should  be  familiar  with  every  part  of  their  instrument 
and  capable  of  its  perfect  adjustment  and  care. 


GUN   POINTERS 

Gun  pointers  should  practice  at  every  opportunity,  what  may  be 
termed  "continual  aim."  The  difficulty  of  keeping  the  gun  pointed 
or  trained  directly  at  the  required  point  on  the  target  can  only  be 
overcome  by  practice  on  the  part  of  the  gun  pointer  (and  the  traversing 
detail  if  the  gun  is  not  operated  by  electricity). 

In  vertical-base  tracking  they  should  keep  the  horizontal  cross-wire 
of  the  sight  constantly  on  the  water  line  of  the  target,  as  explained 
in  the  article  on  position  finders  (see  Chapter  VII) ,  and  the  vertical 
cross-wire  slightly  forward  of  the  point  it  is  desired  to  hit. 

Care  should  be  exercised  in  firing  service  charges,  to  give  the 
command  "Fire"  (when  not  firing  electrically)  when  the  vertical  cross- 
wire  is  a  shade  in  advance  of  the  point  it  is  intended  to  hit,  for  the 
reason  that  there  is  an  appreciable  interval  of  time  between  the  instant 
the  command  "Fire"  is  given  and  the  instant  the  projectile  leaves  the 
muzzle,  caused  by  the  slow  ignition  of  smokeless  powder  as  well  as  the 
time  incidental  to  the  pulling  of  the  lanyard.  This  interval  is  calculated 
at  from  one-sixteenth  to  one  and  one-quarter  seconds,  hence  with  a 
rapidly  moving  target  a  slight  percentage  of  accuracy  is  lost. 

When  the  gun  is  fired  electrically  the  percentage  of  time  lost  is, 
of  course,  reduced  to  the  interval  consumed  by  the  ignition  of  the 
powder. 

In  order  that  accurate  results  may  be  obtained  gun  pointers  should 
be  careful  to  fire  the  gun  at  the  last  stroke  of  the  time  interval  bell 
following  the  range  setter's  announcement  "Range  Set,"  as  the  calcula- 
tions are  based  on  the  projectile  leaving  the  muzzle  at  that  instant. 


RANGE   SETTERS 

The  principal  duty  of  the  range  setter  is  the  accurate  setting  of  the 
range  drum.     He  is  responsible  for  the  proper  elevation  or  range  of  the 


544  THE   SERVICE   OF  COAST  ARTILLERY 

piece.     In  case  an  observation  is  lost  he  sets  the  gun  at  the  range  called 
to  him  by  the  operator  at  the  time-range  board. 

In  setting  for  elevation,  the  effects  of  backlash  are  practically 
eliminated  if  the  graduation  is  always  approached  from  the  same 
direction — that  direction  which  depresses  the  piece  being  the  best. 


METEOROLOGICAL   OBSERVERS 

The  meteorological  observer  is  responsible  for  the  care  and  adjust- 
ments of  all  instruments  and  equipment  installed  at  the  meteorlogical 
station. 

Upon  his  arrival  at  the  station  he  reports  his  presence  to  the  battle 
commander's  station.  He  then  adjusts  the  mercurial  barometer  by 
means  of  the  adjusting  screw  which  lowers  the  mercury  in  the  cistern 
and  then  raises  it  -until  the  surface  exactly  touches  the  ivory  point. 
He  then  tests  the  aneroid  barometer  by  carefully  comparing  its  reading 
with  the  mercurial  barometer  in  order  to  determine  the  proper  correction 
to  be  applied  for  instrumental  error  and  then  notes  the  corrections  to 
be  made  if  any.  He  then  connects  the  electrical  device  of  the  ane- 
mometer, adjusts  the  stop-watch  device,  if  it  is  used  in  the  station. 
He  notes  whether  the  wind-vane  works  freely.  He  tests  and  syn- 
chronizes the  aeroscope.  After  satisfying  himself  that  everything  is 
in  readiness  he  reports  to  the  battle  commander's  station: 

"Meteorological  Station,  In  Order." 

He  then  immediately  records  on  the  aeroscope  the  azimuth  of  the 
wind  as  determined  by  the  wind  vane,  and  its  velocity,  as  determined 
from  ten  readings  of  the  anemometer;  then  reads  the  barometer  and 
thermometer  and  records  on  the  aeroscope  the  atmosphere  per -cent, 
as  determined  from  the  atmosphere  board. 

The  direction  and  velocity  of  the  wind  should  be  recorded  at  least 
every  twenty  minutes  or  oftener  if  necessary.  Any  sudden  change 
either  in  direction  or  velocity  of  the  wind  of  any  considerable  magnitude 
should  be  recorded  and  reported  at  once.  The  relative  weight  of  the 
air  should  be  recorded  whenever  it  changes  more  than  1  per  cent. 
He  keeps  a  complete  record  of  all  messages. 

Meteorological  observers  should  study  carefully  the  description, 
etc.,  of  instruments  appertaining  to  the  station  which  appears  in  another 
part  of  this  book. 


POINTS   FOR  COAST  ARTILLERISTS  545 


TIDE    OBSERVERS    » 

The  tide  observer  is  responsible  for  the  care  and  adjustment  of 
all  equipment  installed  at  the  tide  station. 

Upon  arrival  at  the  station  he  first  tests  and  synchronizes  the 
aeroscope,  and  sees  that  the  tide-gauge  is  in  proper  order.  After 
satisfying  himself  that  everything  is  in  order  he  reports  to  the  battle 
commander's  station: 

"Tide  Station,  In  Order/' 

He  then  records  the  height  of  tide  on  the  aeroscope  and  thereafter 
reports  the  tide  for  every  half  foot. 


CAMP  SANITATION 

Deaths  from  sickness  have  outnumbered  those  of  violence  in  all  our 
wars.  In  the  Philippines,  in  the  eighteen  months  following  July  1, 
1898,  36  officers  and  489  men  were  killed  in  action  or  died  of  wounds, 
while  16  officers  and  693  men  died  of  disease. 

Coast  artillery  camps  are  practically  permanent  and  have  the 
advantage  of  being  pitched  near  tide  or  salt  water.  They  have  more 
or  less  permanent  drainage  and  are  usually  adjacent  to  permanent 
military  hospitals.  All  these  features  facilitate  proper  sanitation. 
They  do  not  necessarily  conduce  to  the  health  of  troops,  however, 
unless  their  features  are  developed  by  the  constant  efforts  of  the 
officers  in  immediate  control  of  troops.  The  importance  of  such 
officers  making  every  effort  to  compel  soldiers  to  comply  with  the  laws 
of  sanitation  is  emphasized  when  it  is  remembered  that  the  whole 
military  fabric  rests  upon  the  physical  character  of  the  individuals 
composing  it. 

Coast  artillery  camps  should  be  as  widespread  as  tactical  con- 
siderations and  convenience  to  the  batteries  will  permit. 

The  health  of  all  camps  depends  fundamentally  upon:  (1)  food, 
(2)  water  supply,  (3)  disposal  of  excreta,  (4)  absence  of  flies  and  other 
germ-carrying  insects,  and  (5)  personal  cleanliness. 

Field  cooking  is  of  the  utmost  importance  to  the  health  and  con- 
tentment of  a  command.  It  is  useless  to  expect  men,  however  well 
equipped,  to  keep  the  field  with  vigor  if  they  cannot  subsist  on  the 
food  supplied.  Officers  should  personally  inspect  each  meal  and  satisfy 


546  THE   SERVICE   OF   COAST   ARTILLERY 

themselves  that  the  food  is  properly  cooked  and  served  in  the  proper 
proportion. 

Civilian  cooks  of  militia  companies  should  be  informed  when  em- 
ployed that  they  will  be  required  to  submit  to  daily  inspection  as  to 
the  cleanliness  of  their  persons,  underclothing,  etc.  The  cleanliness 
of  these  cooks  should  be  a  charge  of  the  company  officers,  for  it  is  a 
well-known  fact  that  civilian  cooks  and  their  assistants  are  usually 
the  most  unkempt  individuals  in  the  camp,  while,  by  reason  of  their 
occupation,  they  should  be  the  cleanest  and  neatest  in  appearance. 

The  water  supply  should  be  given  careful  study,  and  under-drainage 
procured  if  possible.  Proper  drainage  is  an  important  element  in 
connection  with  the  health  of  troops. 

Constant  endeavor  should  be  made  to  prevent  flies  from  carrying 
contagion  from  the  sinks  to  the  food.  Burning  a  little  mineral  oil  in 
the  sinks  and  metal  garbage  cans  helps  keep  down  the  flies.  Garbage 
cans  should,  when  practicable,  be  placed  in  a  shaded  place.  Tightly 
fitting  covers  are  absolutely  necessary.  Lime  when  issued  should  be* 
sprinkled  freely  about  the  cans,  and  after  emptying,  lime  should  cover 
the  bottom  of  each  can.  All  refuse  should  be  burned  and  particular 
care  exercised  to  keep  the  camp  clear  of  horse  manure,  which  is  a  rapid 
breeder  of  flies. 

Company  kitchens  should  be  the  special  care  of  the  officers  of  each 
company,  who  should  visit  them  frequently  and  insist  upon  absolute 
cleanliness  of  every  part  thereof.  They  should  be  well  screened  with 
wire  netting.  All  food  should  be  kept  constantly  covered,  and  when  no 
ice  is  provided  the  meat  ration  should  be  cooked  as  soon  as  received. 
When  ice  is  issued  or  provided  the  meat  ration  should  not  be  allowed 
to  remain  uncooked  for  over  five  hours  after  issue. 

The  only  practical  way  of  ridding  kitchens  and  mess  shacks  of  flies 
is  to  starve  them,  and  this  can  only  be  accomplished  by  keeping  the 
shacks  barren  of  food  particles.  Orders  should  be  issued  prohibiting 
the  throwing  of  food  of  any  character  on  the  ground,  and  severe  pun- 
ishment follow  any  infraction  of  the  order.  Mess  tables  should  be 
cleaned  or  washed  of  all  crumbs  and  refuse  immediately  after  each 
meal  and  the  ground  about  the  mess  tables  raked  and  cleaned  of  all 
crumbs,  etc. 

The  latrines  should  be  kept  scrupulously  clean  and  well  supplied 
with  paper  and  lime.  They  should  be  under  the  charge  of  an  enlisted 
man  held  responsible  for  their  condition  during  his  tour  of  duty. 
This  detail  should  be  indeterminate  in  duration,  that  is,  any  man  found 
or  reported  breaking  any  of  the  rules  governing  the  latrines  should 


POINTS  FOR  COAST  ARTILLERISTS  547 

be  assigned  immediately  to  the  work  of  keeping  them  clean,  such 
assignment  continuing  until  some  other  man  is  found  to  have  trans- 
gressed the  rules. 

Tents  should  be  ditched  as  soon  as  they  are  pitched.  No  circum- 
stance, even  that  of  extreme  fatigue,  should  be  allowed  as  an  excuse 
for  omitting  this  important  part  of  the  proper  pitching  of  tents.  The 
ditch  should  be  dug  around  each  tent  and  should  be  shallow;  the 
earth  taken  out  being  banked  on  the  inner  side,  so  that  the  wall  of  the 
tent  will  fall  over  the  mound.  'The  ditch  should  empty  into  a  com- 
pany ditch  arranged  for  a  careful  system  of  drainage. 

Tent  walls  should  be  raised  for  several  hours  each  day  and  all 
bedding  and  other  contents  exposed  to  the  sun.  If  board  floors  are 
used,  the  boards  should  be  loose  and  removed  frequently  and  the 
ground  beneath  them  cleaned  and  aired.  In  the  case  of  conical  tents 
they  should  be  unfastened  daily  and  folded  loosely  about  the  center 
pole  so  that  the  ground  or  flooring  is  exposed  to  the  sun. 

When  practicable  tents  should  be  pitched  at  such  a  distance  apart 
as  to  have  adjacent  to  each  an  equal  unoccupied  area,  so  that  their 
position  can  be  changed  from  one  site  to  the  other  once  each  week. 

The  Conical  Wall  Tent  contains  a  floor  space  of  212  square  feet; 
air  space,  1450  feet;  allowance,  20  foot  soldiers,  comfortable  for  about 
half  that  number.  When  cots  are  used  6  men  can  be  accommodated. 

The  Wall  Tent  contains  a  floor  space  of  81  square  feet;  air  space, 
500  feet;  usually  used  for  one  or  two  officers. 

The  Common  Tent  contains  a  floor  space  of  57  square  feet;  air 
space,  250  feet;  allowance  6  foot  soldiers,  comfortable  for  half  that 
number. 

Mosquito  netting  is  a  required  sanitary  precaution  against  malaria 
where  the  anopheles  mosquito  is  found  and  is  still  more  important 
against  yellow  fever  within  the  habitat  of  the  stegomyia  fasciata. 
In  such  regions  its  careful  use  should  be  enforced  as  a  matter  of 
routine  discipline. 

Men  should  be  required  to  keep  the  hair  short  and  the  teeth  clean; 
to  bathe  daily  the  head,  feet,  armpits,  groins,  anus,  and  genitals. 


SHIP  BARK  BARKENTINE  BRIG  BRIGANTINE      SCHOONER         SLOOP 


DO 


INDEX 


(Numbers  refer  to  pages.) 


"A"  row,  1,  79. 
Abatis,  1. 
Abbreviations,  63. 
Absolute  deviation,  1. 
Accumulator  room,  1. 
Accuracy  of  D.  P.  F.,  311. 

of  fire  and  practice,  100,  521. 
Adjutant,  1. 

Administrative  organization,  76. 
Aeroscope,  1,  343,  344. 
Aiming,  1,  99. 
Air  spaces,  1. 
All-round-fire,  1,  188. 
Ammunition,  1,  245,  491. 

hoist,  1. 

recess,  1. 

shoes,  2. 

truck,  2,  510. 
Anemometer,  2,  356. 
Aneroid  barometer,  2,  355. 
Angles,  etc.,  106. 

acute,  106. 

biting,  95. 

clear,  502. 

equilateral,  106. 

iscosceles,  106. 

obtuse,  106. 

of  departure,  2,  96. 

of  depression,  96. 

of  elevation,  22,  502. 

of  fall,  2,  96,  502. 

of  impact,  2,  95. 

of  incidence,  2,  95. 

of  jump,  2,  95. 

of  position,  2,  96. 

quadrant,  2,  95,  96,  395. 

right,  106. 

scalene,  106. 

striking,  2,  95,  96,  274. 
Angular  elevation  or  depression,  2,  95, 

96,  395. 

Angular  velocity,  2. 
Approaches,  2. 


Apron,  2. 

Arbitrary  correction,  531. 

deflection  board,  340. 

rapid-fire  guns,  531. 
Arc,  2. 
Area,  2. 
Armament,  2,  107. 

intermediate,  32,  133. 

primary,  45,  108. 

secondary,  52,  155. 
Armor,  2. 

belt,  2. 

piercing  projectiles,  3,  274. 
Armstrong  guns,  3. 

4.72-inch,  153. 

6-inch,  133. 
Artillery,  3. 

garrison,  5. 
Artillery  district,  3. 

adjutant,  3. 

commander,  3. 

commander's  flag,  26. 

engineer,  21. 

ordnance  officer,  4. 

quartermaster,  4. 
Assembling  breech  mechanism: 

12-inch  gun,  see  10-in.  G. 

12-inch  mortar,  118. 

10-inch  gun,  124,  130. 

8-inch  gun,  see  10-in.  G. 

6-inch  gun,  142,  147. 

5-inch  gun,  152. 

3-inch  gun,  159,  162. 

2.24-inch  gun,  167,  171,  176. 
Assistant  plotter,  78. 
Attacks  from  sea,  68. 

night,  74. 

Atmosphere  board,  5,  358. 
Automatic  firing,  5. 

machine  guns,  5. 
Auxiliary : 

horizontal  base  system,  5. 

power  plant,  5. 

549 


550 


INDEX 


Axial  vent,  5. 
Axis,  5. 

of  gun,  5. 

of  trunnions,  5. 
Azimuth: 

correction  scale,  317 

determination  of,  440. 

difference,  5. 

instrument,  5,  314. 

of  a  point,  5. 

of  wind,  62,  98,  341. 

setter,  5. 

"  B  "  row,  5,  79. 
Backlash,  5. 
Bale,  5. 
Ballistic  board,  5. 

corrections,  533. 

coefficient,  97. 

formulas,  101,  104. 

symbols,  101. 

tables,  5. 
Ballistics,  6,  79. 

exterior,  79,  93. 

interior,  79,  89. 
Bandoleer,  6. 
Banjo,  112. 
Banquette,  6. 

tread,  6. 

Bar  and  drum  sight,  6,  133,  360. 
Barbette,  6. 

carriages,  12,  188. 
Barometer,  6. 

aneroid,  355. 

mercurial,  354. 
Base-end  stations,  6. 
Base: 

fuse,  6,  290. 

line,  6,  432. 

ring  test,  506. 
Battery,  6. 

commander,  6,  504. 

commander's  action,  499,  534. 

commander's  station,  7. 

commander's  walk,  7. 

emplacement  book,  7. 

field  of  fire,  7. 

fire  control,  25. 

in  commission,  31. 

in  service,  31. 

location  of,  431. 

manning  table,  7. 

out  of  commission,  40. 

out  of  service,  40. 

parade,  7. 


Battery,  subcaliber  practice  186,  534. 

target  practice,  504,  533. 
Battle: 

area,  7. 

chart,  7. 

command,  8,  496. 

command  drill,  496. 

commander,  8,  496. 

commander's  station,  8. 

flag,  8. 

ships,  8. 

tactics,  9. 
Berm,  9. 
Bevel  gear,  106. 

wheel,  9. 
Biting  angle,  95. 
Bivouac,  9. 
Black  charcoal  powder,  245. 

prismatic  powder,  250. 
Blank  ammunition,  260,  492. 
Blank  charges: 

weight  of,  262. 
Blast  slope,  9. 
Blasting  gelatine,  9,  269. 
Blending  powder,  9,  258,  512. 

room,  9. 
Blind  shell,  9. 
Blocks  and  tackles,  470. 
Boat  drill,  428. 
Boat  telephone,  9,  423. 
Bomb,  9. 

proof,  9. 

Book,  emplacement,  22. 
Booth,  9;  510. 
Bore,  9,  82,  510. 

bottom  of,  9. 

length  of,  9,  Chap.  V. 

plug,  9. 

sighting,  9,  454,  506. 
Bound,  9. 
Bourrelet,  9,  511. 
Brackets,  9. 
Breech,  9. 

block,  10,  82,  509. 

bushing,  10,  79. 

detail,  10. 

face  of,  10. 

plate,  84. 

recess,  10,  80. 

reinforce,  10,  80. 
Breech  mechanisms,  10.  82. 

Driggs-Schroeder,  173. 

Drop-block  system,  164. 

Interrupted  screw,  82,  120. 

Interrupted  thread,  169. 


INDEX 


551 


Breech  Mortar,  112,  113. 

Stockett,  126. 

6-in.  Q.  F.  Armstrong,  133. 

6-in.  R.  F.  G.,  M.  1897  Mi,  136. 

6-in.  R.  F.  G.,  M.  1903,  143. 

5-in.  R.  F.  G.,  M.  1897,  149. 

4.72-in.  Q.  F.  Armstrong,  153. 

3-in.  D.-S.  G.,  M.  1898,  155. 

3-in.  R.  F.  G.,  M.  1902,  160. 

2.24-in.  D.-S.,  M.  1898,  164. 

2.24-in.  D.-S.,  M.  1900,  168. 

2.24-in.  Am.  Ord.,  173. 
Brown  charcoal  powder,  250. 

prismatic  powder,  10,  251,  256. 
Brown  &  Sharpe  micrometer,  389. 
Buffer  valve,  227. 

Building-up  charges,  10,  257,  258,  512. 
Built-up  cannon,  10,  80,  86. 
Buoy,  10. 

Bursting  charge,  10,  Chap.  V. 
Butt,  10. 
Button-drill  primer,  10,  282. 

"C"  row,  10,  79. 

Cake  powder,  10,  248,  249. 

Caliber,  10. 

Calibration,  10,  524. 

Call  to  arms,  11. 

Cam  wheel,  106. 

Cam  lever  grip,  106. 

Camera,  526. 

Camp  sanitation,  545. 

Cannister,  11,  278. 

Cannon,  11  (see  Guns). 

ball,  11. 

powder,  11. 
Cannonade,  11, 
Cannoneer,  11. 
Canopy,  11. 
Cap-square,  11,  111. 
Capital,  11. 

Capped  projectile,  11,  272. 
Carriages,  11,  187. 

A.  R.  F.,  188. 

barbette,  12,  188. 

barbette  proper,  1SS. 

casemate,  12,  188. 

coast,  12,  187. 

disappearing,  12,  188,  199. 

fixed,  12,  187. 

L.  F.,  188. 

masking  mount,  12,  188,  228. 

mortar,  188,  236. 

movable,  12,  169. 

pedestal  mount,  188,  192. 


Carriages,  parapet  mount,  232. 

rapid-fire  gun,  12,  160. 

recoil  cylinders  of,  204,  238. 

special,  188,  197. 

wheeled,  168. 
Cartridge,  12. 

bags,  12,  259. 

extractor,  12. 

for  small  arms,  491. 

room,  12. 
Case,  12. 
Case  I,  12,  99. 

II,  12,  100. 

III,  12,  100. 
Casemate,  12. 

battery,  12. 

carriages,  188. 

electrician,  12,  78. 

officer,  13. 
Casernes,  13. 
Cast-iron  shot,  13,  276. 
Castramentation,  13. 
Cathead,  13. 
Center  of  gravity,  13,  94. 

band,  13,  276. 

of  cannon,  13. 

of  impact,  13,  523,  530. 

pintle,  13,  188,  445. 
Centering  slope,  13,  82. 
Centigrade  scale,  353. 
Centrifugal  force,  13,  295. 

fuses,  13,  295. 
Chamber,  13. 

powder,  44,  82. 

shot,  54,  82. 
Charcoal  powder,  245. 
Charge,  13,  520. 
Charts,  13,  304. 

battle,  7. 

difference,  20. 

harbor,  30. 

powder,  45,  400. 

symbol,  56. 
Chase,  13,  82. 
Chassis,  13,  203. 
Chief-loader,  13,  78. 

of  ammunition  service,  14. 

of  coast  artillery,  14. 

of  coast  artillery's  flag,  14. 

planter,  14,  78. 
Chronograph,  14. 
Chronometer,  14. 
Circle,  14,  106. 
Circuit-closer,  14. 
Circumference,  14. 


552 


INDEX 


Civilian  cooks,  546. 
Cleaner,  14. 
Clear  angle,  502. 
Clinometer,  14,  506. 

rest,  14. 
Coast  Artillery: 

board,  14. 

chief  of,  14. 

company,  14. 

corps,  66,  76. 

fort,  15. 

garrison,  15. 

material,  15. 

memorandum,  505,  537. 

posts,  15. 

reserves,  15,  66,  76,  77,  494. 

supports,  15,  66,  76. 
Coast  defense,  15. 

officer,  15. 

principles  of,  66. 

ships,  15. 

theory  of,  66. 
Coast  Guard,  15. 
Coefficient,  of  efficiency,  90. 

of  form,  98. 

of  useful  effect,  90. 
Collar,  15. 

Collimation,  33,  308. 
Colors,  15. 

of  coast  artillery  corps,  15. 

on  projectiles,  16,  276. 
Combination  electric  friction  primer,  16, 

285. 

Combination  fuse,  16,  297. 
Command : 

administrative,  76. 

appropriate  to  grade,  77. 

tactical,  76. 
Commands : 

of  battery  commander,  534. 

of  battle  commander,  497. 

of  fire  commander,  498. 

searchlight,  502. 
Commissary  sergeant,  16. 
Common  electric  primer,  16,  282. 

friction  primer,  16,  279. 
Communication  officer,  16,  503. 
Communications.  17,  348,  503,  515,  541. 
Composite  artillery  type  telephone,  17, 

346. 

Computer,  17. 
Concentric,  17. 

Conduits,  wiring  and  illumination  of  car- 
riages, 226. 
Cone,  106. 


Cone,  of  dispersion,  17,  522. 

of  spread,  17,  522. 
Conical,  17,  106. 
Console,  17,  106. 
Construction  of  batteries,  431. 
Contact  firing,  17. 
Converted  gun,  17. 
Cordage,  17,  460. 
Cordite,  256. 
Cored  shot,  17. 
Corps  of  engineers,  431. 
Corrected  range,  17. 
Corridor,  17. 

wall,  17. 
Counter,  attack,  17. 

recoil,  17. 

recoil  springs,  240. 

recoil  systems,  194,  204,  240,  508. 
Countermining,  17. 
Counterscarp,  17. 
Counterweight,  17,  209. 

well,  18. 
Cover  post,  18. 
Cradle,  18. 
Crane,  18. 

Critical  dimension,  18,  91. 
Crest: 

exterior,  24. 

interior,  32. 
Cross-fire,  18. 
Crosshead  guides,  203. 
Crow's  nest,  18. 
Cruiser,  18. 
Cruiser  battleship,  18. 
Crusher  gauge,  18,  90,  396,  528. 
Curvature  of  earth,  18,  95,  96,  313. 
Curve,  18. 

of  trajectory,  95,  96. 
Curves,  range  board,  333,  514. 
Cut-off  jack  set,  18,  504. 
Cylindrical,  19,  106. 
Cylindro-conical,  19,  106- 

"D"  row,  19,  79. 
Danger,  range,  19. 

space,  19. 
Data  line,  19. 
Datum  point,  19,  308. 
Defense,  of  coast  line,  66. 

land,  73. 

of  harbors,  66. 

plans,  28,  494. 

zones,  62. 
Definitions,  1. 
i.  ^flection.  19. 


INDEX 


553 


Deflection  board  (gun),  19,  338,  515. 

board  (mortar),  340. 

computer,  78. 

corrections,  338,  340,  505,  515,  532. 

scale,  19. 

value  in  yards,  533. 
Delayed  automatic  firing,  19. 
Delivery  table,  19. 
Density  of  air,  97. 

of  loading,  19,  93,  517,  528. 
Department  artillery  officer,  19. 

commander,  19. 

commander's  flag,  19. 
Depression  position  finder,  19,  304,  513. 

description  of  W.  &  S.,  304. 

description  of  Lewis,  312. 

system,  304. 
Derricks,  476. 

Determining  true  azimuth,  440. 
Detonation,  20. 
Detonating  fuses,  302. 
Deviation,  20. 

absolute,  20. 

at  target,  20,  525. 

mean  lateral,  20. 

mean  longitudinal,  20. 

range,  20. 

Device,  obturating,  35,  115. 
Diameter,  20. 
Difference  chart,  20. 
Direct  fire,  20. 
Directing,  gun,  20,  437. 

point,  20,  437. 

Disappearing  carriage,  20,  199. 
Dismounting  breechblock: 

12-in.  gun  (see  10-in.  gun). 

12-in.  mortar,  117. 

10-in.  gun,  124,  129. 

8-in.  gun,  82. 

6-in.  gun,  142,  147. 

5-in.  gun,  152. 

3-in.  gun,  159;  162,  163. 

2.24-in.  gun,  167,  172,  175. 
Displacement,  20. 

gun,  29. 

of  any  point,  20. 

of  ships,  20. 

Distribution  box,  20,  422. 
District,  (see  Artillery  district). 

artillery  engineer,  21. 

commander,  4. 

drill,  21. 
Ditch,  21. 
Double: 

primary  station,  21. 


Double  secondary  station,  21. 
Drift,  21. 

corrections,  338. 

Driggs-Schroeder  R.-F.  gun,  21,  155. 
Driggs-Seabury  R.-F.  gun,  21,  155,  163, 

168.  232. 
Drill,  494. 

primer,  21,  282. 

regulations,  494. 
Dry  gun  cotton,  263. 
Dummy  charge,  516. 

projectile,  510,  516. 
Dunnite,  21. 
Dynamite,  21,  267. 

Earthworks,  21. 

Ecrasite,  21,  266. 

Eight-inch  gun,  21,  132. 

Elasticity,  21,  87. 

Electric  ballistic  machine,  14. 

controllers,  223. 

firer,  21. 

motors,  219,  223. 

mines,  21,  414. 

primer,  21,  282. 

safety  firing  attachment,  218. 
Electrical : 

elevating  and  depressing,  226. 

retracting,  226. 

traversing,  225. 
Electrician : 

casemate,  78. 

detachment,  21. 

master,  78. 

sergeant,  22,  78. 

Elements  of  trajectory,  93,  95,  96. 
Elevating  system,  200-507. 

friction  device,  507. 
Elevation,  22,  502. 

quadrant,  47,  395. 

setter,  22. 

sight,  54,  359. 
Elliptical,  22. 

Elongated  projectiles,  22,  274. 
Emergency  position  finder,  22. 

station.  22. 

system,  22. 
Emplacement,  22. 

book,  22. 

booth,  510. 

officer,  22,  534. 
Encampment,  545. 
Endurance  of  cannon,  23. 
Energy  of  projectile,  23,  104,  272. 

of  recoil,  23. 


554 


INDEX 


Enfilade  fire,  23. 

Engineer,  23,  78. 

Engineer  corps,  431. 

Engineering,  seacoast,  431. 

Engineer's  transit,  314. 

Equalizing  pipes,  23,  204,  238. 

Erosion  of  the  bore,  23,  109,  112. 

Estuary,  23. 

Exploder,  23. 

Exploders  or  detonators,  270. 

Explosive,  23. 

compound,  24,  251. 

"D",  24,  268. 

house,  24. 

mixture,  24,  251. 
Explosives,  245. 

atlas  powder,  268. 

black  charcoal  powder,  245. 

black  prismatic  powder,  250. 

blasting  gelatine,  269. 

brown  charcoal  powder,  250. 

brown  prismatic  powder,  251,  256. 

charcoal  powder,  245. 

cordite,  256. 

dynamite,  267. 

ecrasite,  266. 

fulminates,  245,  270. 

giant  powder,  268. 

guncotton,  263. 

high,  245,  263. 

Judson  powder,  268. 

low,  245. 

lyddite,  266. 

maximite,  269. 

melinite,  266. 

melting,  266. 

nitrocellulose  powder,  251. 

nitroglycerine,  265. 

picric  acid,  266. 

rendrock,  268. 

shimose,  266. 

smokeless,  251. 

sphero-hexagonal,  55,  250. 

thawing,  266. 

trinitrotoluol,  269. 

vulcan  powder,  268. 
Exterior  crest,  24. 

slope,  24. 
Extreme  range,  24. 

Face  of  breech,  24. 

of  muzzle,  24. 

of  rimbase,  24. 

of  trunnion,  24. 
Fahrenheit  scale,  353. 


Field,  combat,  73. 

of  fire,  24. 

safety  of,  500. 

Fifteen-pounder,  24,  155,  162. 
Fillet,  24. 
Final  velocity,  24. 
Fire,  24. 

accuracy  of,  100. 

all-round,  1,  188. 

ar£a,  24. 

in  field  combat,  74. 

limited,  33,  188. 

observation  of,  531. 

orders  of,  499. 

rate  of,  49. 

restricted,  499. 

unrestricted,  499. 
Firearm,  26. 
Fire  command,  25,  497. 

grouping  batteries  of,  431. 

target  practice  (service),  497. 
Fire  commander,  25,  497,  518. 

appropriate  rank  of,  78. 

assignment  of,  25. 

commands  of,  497. 

duties  of,  25. 
Fire  commanders,  497. 

action,  498. 

plotting  board,  330. 

station,  25. 

supervision  of  target  practice,  500. 
Fire  control,  25. 

apparatus  and  instruments,  304. 

installation,  26. 

range  officer,  537. 

system,  26. 
Fire  left,  26. 

right,  26. 

Fired  standard  primer,  26,  282. 
Firing  attachment,  218,  509. 

interval,  26. 

machine,  26. 

mechanism,  174,  176,  183. 

switch,  safety,  219. 
First-class  gunner,  30,  78. 
First  sergeant,  78. 
Five-inch  gun,  26,  148. 
Fixed  ammunition,  26,  261,  491. 

armament,  26. 

defenses,  26. 

light,  26. 

mount,  26,  188. 
Flag: 

battle,  8. 

garrison,  28. 


INDEX 


555 


Flag  of  admiral  of  the  navy,  26. 

of  artillery  district  commander,  26. 

of  assistant  secretary  of  the  navy,  26. 

of  assistant  secretary  of  war,  26. 

of  chief  of  coast  artillery,  26. 

of  department  commander,  27. 

of  post  commander,  27. 

of  president  of  the  U.  S.,  27. 

of  rear-admiral  of  the  navy,  27. 

of  the  secretary  of  the  navy,  27. 

of  the  secretary  of  war,  27. 

of  the  U.  S.,  27. 

of  vice-admiral  of  the  navy,  27. 

post,  44. 

storm,  55. 

submarine  boat  signal,  56. 
Flags,  27. 
Flagship,  27. 
Flanking  fire,  27. 
Floating  defenses,  27. 
Focussing  telescope,  306. 
Foot-ton,  27. 
Force  of  gravity,  93. 
Forcing,  27. 

cone,  27,  82. 
Formulas,  ballistic,  101. 
Fort  commander,  27. 

record  book,  27. 
Fortified  point,  28. 
Fosse,  28. 

Four-inch  gun,  28,  155. 
Four  point  seventy-two-inch  gun,  3,  153. 
Friction,  28. 

clutch,  213. 

primer,  28,  279. 
From  battery,  28. 
Front  pintle,  28,  188,  445. 
Frontal  attack,  68. 

fire,  28. 
Frustrum,  28. 
Fulcrum,  28. 
Fulminate,  28,  270. 
Fuses,  28,  290. 

base,  290 

combination,  297. 

detonating,  302. 

point,  290. 

Gabion,  28. 
Gallery,  28. 
Galvanometer,  28. 
Garrison,  28. 

coast  artillery,  15, 

flag,  28. 

gin,  28. 


Gas-check  pad,  28,  84. 

seat,  82. 

adjustment  of,  183. 
Gear  wheel,  28,  106. 
General  defense  plans,  28,  494. 

principles,  66. 

Geometrical  magnitudes,  etc.,.  106. 
Gins,  472. 
Glacis,  29. 

Gravemetric  density,  29. 
Gravity,  29,  94. 
Graze,  29. 
Grooves,  29,  87. 
Grouping  batteries,  431. 
Guard  room,  29. 
Gun,  29,  79. 

16-inch,  108. 

14-inch,  109. 

12-inch,  110,  111,  112. 

10-inch,  120. 

8-inch,  80,  132. 

6-inch,  133,  136. 

5-inch,  148. 

4.72-inch,  153. 

4-inch,  155. 

3-inch,  155,  162. 

2.24-inch,  163,  164,  168,  172 

1-pounder,  184. 

6-pounder,  163,  164,  168,  172. 

15-pounder,  155,  162. 

arm,  317. 

automatic,  5. 

boat,  29. 

carriage,  29. 

center,  location  of,  437. 

commander,  29,  78. 

commander's  range  scale,  29. 

company,  29. 

construction,  79,  107. 

cotton,  29,  263. 

deflection  board,  338. 

differences,  29. 

displacement,  29. 

lift,  29. 

machine,  5,  34. 

platform,  29. 

plotting  board,  315. 

pointer,  29,  78,  543. 

powder,  30,  245. 

section,  30. 

semi-automatic,  53. 

sling,  490. 

sub-caliber,  184. 

wire-wound  type,  107. 
Gunner,  30,  78. 


556 


INDEX 


Gunner's  quadrant,  30,  393. 
Gunnery,  30,  79. 
specialists,  30. 

Hang  fire,  30. 
Harbor,  charts,  30. 

defense,  66. 

Height  of  D.  P.  F.,  311. 
High-angle  fire,  30. 
Hitches,  468. 
Hoist,  30. 

ammunition,  1. 

powder,  45. 

room,  30. 

shot,  1. 

Homogeneous,  30. 
Hoop,  30,  79. 
Horizontal,  30. 

angle,  31. 

base-line  measurement,  432. 

base  system,  31,  311. 

plane,  31. 

position  finder,  31,  304,  312. 

range,  31. 

velocity,  31. 
Hostilities,  31. 
Howitzer,  31. 
Hydraulic  jack,  31,  479. 
Hydrographic  surveying,  458. 
Hygrometer,  31. 
Hypothetical  targets,  31. 

Identification  of  target,  31,  503. 
Igniter,  31. 

charge,  31,  259. 
Igniting  primer,  31,  289. 
Illuminating  light,  31,  402. 
Illumination,  conduits  and  wiring,  226. 
In  battery,  31. 
In  commission,  31. 
Independent  action,  499. 
Indication  of  target,  31,  503. 
Indicator: 

aeroscope,  343,  344. 

tide,  304. 

wind  component,  341. 
Infantry,  73. 
Inflammation,  31. 
Initial  pressure,  31. 

of  rotation,  32. 

of  translation,  32. 

velocity,  32. 
Inner  defense  aone,  62. 
In  service,  31. 


Inside  of  a  beam,  32. 
Instruments,  304. 
Intelligence  line,  32,  535. 
Interior  crest,  32. 

slope,  32. 

wall,  32. 

Intermediate  armament,  32,  133. 
Interrupter,  345,  515. 

Jacket,  32,  79. 
Judgment  firing,  32. 
Jump,  angle  of,  32,  95,  507. 
Junction  box,  32,  423. 

Kentledge,  33. 

Knots,  467. 

Laflin  &  Rand  firing  machine,  33. 

Land  attack,  73,  74,  75,  500. 

defense,  73,  500. 

front,  33. 
Landings,  70. 
Lands,  33,  88. 
Lanyard,  33,  217. 
Large  caliber  guns,  33,  107. 
Lateral,  33. 
Latrine,  33. 
Laying,  33,  99. 
Least  dimension,  33,  91. 
Le  Boulenge  chronograph,  33. 
Length  of  the  bore,  33. 
Leveling,  455. 
Levers,  472. 
Limited  fire,  33,  188. 
Limits  of  fire,  33,  62. 
Line,  33. 

of  collimation,  33,  308. 

of  defense,  33. 

of  departure,  33,  95,  102. 

of  direction,  34,  95. 

of  impact,  34,  95. 

of  metal,  447. 

of  shot,  34,  95. 

of  sight,  34,  95. 
Litmus,  34. 

paper  test,  34. 
Loading: 

density  of,  19,  93,  517,  528. 

mines,  421. 

platform,  34. 

position,  34. 

projectiles,  378. 

room,  34,  417,  424. 

tray,  34. 


INDEX 


557 


Location : 

of  batteries,  431. 

of  horizontal  base  lines,  432. 

of  pintle  centers,  438. 

of  target,  34. 

"Long  nose"  projectiles,  274. 
Long  roll,  34. 
Longitudinal,  34. 
Lot  number,  256. 
Lug,  34. 
Lyddite,  34,  266. 

Machine  gun,  34. 

mounts,  34. 

Machinery,  care  of,  424,  481. 
Magazine  rifle,  4X3. 
Magazines,  35,  525,  527. 
Main  bore,  35,  82. 
Maneuver  signals,  539,  540. 
Maneuvering  rings,  35. 
Manning  parties,  35. 

tables,  35. 
Mark  one,  35,  110. 
Marine  obstructions,  35. 
Masking  mount,  35,  22 X. 
Master  electrician,  35,  78. 

gunner,  35,  78. 
Material  target,  35. 
Maul,  35. 

Maximite,  35,  269. 
Maximum,  36. 

ordinate,  36,  95. 

pressure,  36. 

range,  36,  107. 
Mean  lateral  deviation,  36. 

longitudinal  deviation,  36. 
Measure  of  uniformity,  36. 
Mechanic,  36,  78. 
Mechanics,  36,  106. 
Medium  caliber  guns,  36,  107,  133. 
Melinite,  36,  266. 
Melting  explosives,  36,  266. 
Mensuration,  36. 
Mercurial  barometer,  36,  35 

thermometer,  58,  354. 
Meteorological'  message,  36. 

observer,  36,  78,  541. 

station,  37,  544. 
Methods  of  pointing,  99. 
Micrometer,  37. 

caliper  or  gauge,  37,  396. 
Military  crest,  37. 
Mine  (submarine),  37,  414. 

field,  37. 

material,  care  of,  424. 


Mine,  planter,  38,  422. 

plotting  board,  328. 

prediction  ruler,  329. 
Mine  command,  37. 

boat  drill  for,  428. 

fire-command  system,  417. 
Mine  commander,  37,  414. 
Mine  company,  37,  424. 
Mine-field  lights,  37. 

officer,  38. 

Mining  casemate,  38,  417. 
Minus  correction,  38,  384. 

deflection,  38,  384. 
Misfire,  38. 
Miter  wheel,  38. 
Moat,  38. 
Mobile,  army,  67,  76. 

torpedo,  38,  414. 
Monitors,  38. 
Mortar,  38,  112,  119,  120. 

arm,  325. 

battery,  38. 

breech  mechanism,  114. 

carriage,  236. 

cast-iron,  112. 

company,  38. 

deflection  board,  340. 

pit,  38,  112. 

plotting  board,  324. 

predicter,  326. 

steel,  119. 

velocities,  327. 

wire- wound  type,  107. 

zones,  62,  327. 
Motor  generator,  224. 
Motors,  223. 

Mount  (see  Carriage),  38. 
Mounting  cannon,  38. 
Movable  armament,  39,  168. 

carriage,  39,  188. 
Multiplying  scale,  338. 
Mushroom  head,  39. 
Musician,  78. 
Muzzle,  39. 
Muzzle  velocity,  39,  519. 

probable,  for  trial  shots,  519. 

variations  in,  519. 

Naval  attack,  68. 
Night,  attacks,  74. 

signals,  542. 

Nitrocellulose  powder,  39,  251. 
Nitroglycerine,  39,  265. 
Non-commissioned  officers,  39,  78. 
Nose,  39. 


558 


INDEX 


Object  glass,  39,  306. 
Oblique  fire,  39. 
Observation,  firing,  39. 

of  fire,  531. 

telescope,  39. 

Observations  with  D.  P.  F.,  310,  311. 
Observer,  39,  78,  535,  542. 

1st  and  2d  class,  78. 

meteorological,  78,  544. 

tide,  78,  545. 

tug,  536. 
Observing  interval,  39. 

room,  39. 

station,  39. 

Obturating  primer,  39,  274. 
Obturator,  39,  115,  509. 

head,  39. 
Occult  light,  39. 
Offensive  return,  39. 
Officers,  points  for,  494. 
Ogive,  40,  272. 
Oil  room,  40. 
Oils,  40,  425. 
Okonite  joint,  420. 
Omniscope,  40. 
One-pounder,  40,  184. 
Open  sight,  40,  359. 

bar  and  drum,  6,  133,  360,  363. 

2.24-inch  (6-pounder),  359. 

3-inch  (15-pounder),  360. 

4-inch,  360. 

4.72-inch,  360. 

5-inch,  361. 

6-inch,  360. 

8-,  10-,  and  12-inch,  361. 
Opposite  angles,  40. 
Orderly,  78. 
Orders,  496. 

of  fire,  40.  499. 
Ordnance,  40. 

machinist,  40. 

officer,  40. 

sergeant,  40. 

Organization  and  personnel,  76. 
Orientation,  40,  449. 

table,  40. 

Out  of  commission,  40. 
Out  of  service,  40. 
Outer  defense  zone,  62. 
Outposts,  40. 
Outside  of  the  beam,  40. 
Overs  and  shorts,  527. 

Paint  mixtures,  etc.,  425. 
Paints,  oils,  etc.,  425. 


Paints  on  projectiles,  41.  276. 

Pantograph,  41. 

Parade  slope  or  wall,  41. 

Parados,  41. 

Parallax,  41,  307. 

Parallel,  41. 

Parapet,  41,  533. 

Patrol  boats,  41. 

Pawl,  41,  106. 

Pedestal  mount,  192. 

Penetration  of  projectiles,  41,  109    272, 

273,  277. 
Percussion  cap,  42,  287. 

fuse,  42,  291. 

primer,  42,  286. 
Periscope,  42. 

Permanent  fortifications,  431. 
Perpendicular,  42. 
Personnel,  42,  76,  77,  515. 
Picket  boats,  42. 
Picric  acid,  42,  266. 
Piece  (see  Gun),  42. 
Pintle  centers,  location  of,  188,  445. 
Pipe,  equalizing,  23,  204,  238. 
Pit,  42. 

commander,  42. 

mortar,  112. 
Plan  of  land  defense,  73. 
Plane,  42. 

of  departure,  42,  95,  98. 

of  direction,  42,  95.  98. 

of  sight,  42,  95,  98. 
Plans,  general  defense,  28,  494. 
Planter.  42,  422. 
Planting  mines,  422. 

section,  42. 
Platen  scale,  338. 
Plotter,  42,  78,  535. 
Plotting  board,  42,  314,  514. 

fire  commander's,  328. 

gun,  315. 

mortar,  324. 

submarine,  328.      ^ 
Plotting  room,  43. 
Plunging  fire,  43. 
Plus  correction,  43,  384. 

deflection,  43,  384. 
Point,  43. 

directing,  20,  437. 

fuse,  43,  290. 

of  fall,  43,  93,  95,  96,  502. 

of  impact,  43,  95. 
Pointing,  43,  99. 
Points  for  artillerists,  494. 
Polaris,  442. 


INDEX 


559 


Position,  angle,  43. 

finder,  43,  304. 
Position-finding   system,   43,    310,    311, 

513. 
Post: 

adjutant,  43. 

artillery  engineer,  43. 

commander,  44. 

commander's  flag,  44. 

commissary  sergeant,  44. 

flag,  44. 

non-commissioned  staff,  44. 

ordnance  officer,  44. 

quartermaster,  44. 

quartermaster  sergeant,  44. 

telephone  switchboard,  44. 
Powder  (see  Explosives),  44,  512,  527. 

blast,  44. 

blending  of,  258. 

cases,  44. 

chamber,  44,  82. 

charges,  table  of,  255. 

chart,  45. 

chute,  45. 

hoist,  45. 

hoist  well,  45. 

magazine,  45. 

power  expansive  force,  90. 

room,  45. 

section,  259. 

test,  litmus,  34,  104. 
Powder  charge: 

preparation  of,  9,  258,  512,  517. 

sections  of,  259. 

table  of,  255. 

weights  of,  104,  259. 
Power  and  light  equipment,  45. 

room,  45. 

section,  45. 

station  or  plant,  45. 
Practice  (see  Target  practice). 
Practice,  accuracy  of,  100. 
Predicted  firing,  45. 

point,  45. 
time,  45. 

Predicting  interval,  45. 
Predictor,  45. 
Preponderance,  45. 
Preparation  of  charges,  9,  25X.  512,  517. 

of  paints,  425. 
Pressure  cylinders,  45,  397. 
Pressure  gauge,  45,  397. 
Primary  arm-setter,  78. 
armament,  45,  108. 
station,  45. 


Primer,  46,  279. 
Priming  charges,  46,  259. 
Principles  of  coast  defense,  66. 
Prismatic  powder,  46,  250,  251. 
Probability  factors,  46. 

of  error,  46,  522. 
Probable  error  card,  522. 

muzzle  velocity,  519. 

zone,  46,  522. 
Profile  board,  46. 
Progressive  powder,  46,  245. 
Projectile,  46,  93. 

in  the  gun,  89. 

in  its  flight,  93. 
Projectiles,  271,  511,  528. 

armor  piercing,  274. 

capped,  273. 

cast-iron,  276. 

deck  piercing,  274. 

dummy,  510,  516. 

energy  of,  272. 

filled  and  fused,  268,  278. 

long  nosed,  274. 

painting  of,  276. 

penetration  of,  41,  109,  272,  273,  277. 

seating  of,  516. 

storage  of,  278. 

travel  of,  59,  517. 
Projector,  46. 
Proof,  of  gunpowder.  46. 

plug,  46,  396. 
Property  officer,  46. 
Protractor,  47. 
Pyramidal  target,  47. 

Quadrant,  47,  393,  509. 

angle  of  departure,  47,  96. 

elevation,  47,  395. 

elevation  scale  test,  506. 
Quartermaster,  47. 

sergeant,  47,  78. 
Quick-firing  guns,  47,  133,  153. 
Quickness  of  burning,  47. 

Rack,  47. 
Radial  vent,  47. 
Radius,  47. 

Rake  (see  Range  rake). 
Rammer,  47,  517. 
Ramp,  47. 
Rampart,  47. 
Range,  47. 

azimuth  table,  48. 

board,  48,  332,  514. 

correction  computer,  78. 


560 


INDEX 


Range,  corrections,  332,  514,  532. 

danger,  501. 

deviation,  48,  527. 

difference,  48. 

finder,  48,  304. 

finding  system,  304. 

keeper,  48,  78. 

of  a  shot,  49. 

of  ballistic  tables,  48,  96. 

officer,  48,  515,  518,  535. 

rake,  48,  525. 

scale,  49. 

searchlight,  406. 

setter,  49,  78,  534. 

station,  518 

table,  49. 
Rapid-fire  gun.  49,  142. 

carriage,  49,  192. 
Rate  of  fire,  49. 
Rated  men,  78. 
Ratings,  49,  78. 
Reader,  49,  78. 
Rear  slope,  49. 
Receiving  table,  49. 
Recoil,  49. 

cylinders,  49,  189,  199.  508. 

systems,  194,  204,  238,  508. 
Reconnaissance,  49. 

in  force,  49. 
Record  practice,  505. 
Recorder,  49,  78,  498. 
Records  of  firings,  50,  528. 
Rectangular  target,  50. 
Redoubt,  50. 
Reference  numbers,  50. 
Reflected  ray  or  beam,  404. 
Regulations,  50. 
Reinforce,  50. 
Relay,  50. 

Relocation  of  target,  50. 
Remaining  velocity,  50. 
Reserve  table,  50. 

Reserves,  coast  artillery,  15,  76,  77,  494. 
Resistance  of  the  air,  50,  93. 
Restricted  fire,  50,  499. 
Retardation,  50. 
Retractor,  50. 
Reverse  fire,  50. 
Ricochet,  50,  501. 
Rifle  (see  also  Gun),  50. 
Rifling,  51,  82,  87. 
twist  of,  60,  87. 
Rimbases,  51. 

Ring  resistance  fuse,  51,  291. 
Roadstead,  51. 


Rocket,  51. 

Ropes,  460. 

Rotating  band,  51,  82,  511. 

Rotation,  51. 

Rotation  of  projectile,  51. 

Round,  51. 

Roving  light,  51. 

Row,  51. 

Rubber  impression  of  bore,  51. 

Run  by,  69. 

Safety-firing  switch,  219. 
Safety  lanyard,  51,  217. 
Safety  officer,  501,  536. 
Salvo,  51. 

fire,  51,  499. 

point,  51. 

table,  51. 
Sanitation,  545. 
Scarp,  51. 
Scout  ships,  51. 
Screw  box,  51. 
Seacoast  engineering,  431. 
Searchlight,  51,  402. 

arc,  410. 

area,  52,  402. 

carbons,  413. 

classification  of,  407. 

commands,  502. 

effective  ranges,  406. 

essentials  of  effectiveness,  412. 

lamp  mechanism,  408. 

mirror,  411. 

nomenclature,  407. 

observer,  52. 

officer,  52. 

operator,  52,  78. 

range,  52,  406. 

tactical  location,  402. 

types  of,  404. 

tower,  52. 

watcher,  78,  406. 
Seat  of  the  charge,  52,  517. 
Secondary  armament,  52,  155. 

arm-setter,  78. 

or  auxiliary  power  plant,  52. 

station,  52. 

Second-class  gunner,  78. 
Sector  of  explosion,  53. 
Segment,  53. 
Self-contained  horizontal  position  finder, 

53. 

Semi-automatic  guns,  53. 
Separate  observing  room,  53. 

plotting  room,  53. 


INDEX 


561 


Sergeant-major,  53,  78. 
Service,  charge,  53,  255. 

practice,  505. 
Serving  table,  53. 
Serving  the  vent,  53. 
Set-back  point,  53. 
Set-forward  point,  53. 
Set-forward  ruler,  53. 
Shears,  53,  474. 
Shell,  53,  274. 

armor  piercing,  274. 

deck  piercing,  274. 

filler,  54. 

room,  54. 

torpedo,  59,  275,  276. 

tracer,  54. 

Shimose  powder,  54,  266. 
Shore  signals,  538. 
Shot,  54,  274,  276. 

armor  piercing,  274. 

cast-iron,  274. 

chamber,  54,  82. 

gallery,  54. 

hoist,  54. 

hoist  well,  54. 

penetration  of,  109,  277. 

room,  54. 

tongs,  54,  516. 

trucks,  192,  510. 
Shrapnel,  54,  278. 
Sights,  54,  168,  359. 

deflection,  54. 

elevation,  54. 

standard,  54,  506. 

telescopic,  57,  168,  361. 
Signal  rocket,  54. 

station,  54. 

Signals,  at  target  practice,  538. 
Signs,  65. 

Six-inch  gun,  54,  133,  136. 
Six-pounder,  54,  163. 
Small  arms,  483. 

ammunition,  491. 

boats,  54,  427. 

caliber  guns,  54,  155. 

landing  parties,  75. 
Smokeless  powder,  54,  251. 
Smooth-bore  cannon,  54. 
Sound,  signals,  540,  541. 

travel,  55. 

Sources  of  error,  505. 
Special  mounts,  197. 
Specific  gravity,  55. 
Sphero-hexagonal  powder,  55,  250. 
Splices,  462. 


Spline,  55,  106. 
Sponge,  55. 

Sprocket  wheel,  55,  106. 
Spur  ring,  55. 

wheel,  55,  106. 
Staff  officers,  55,  77,  78 
Stand  fast,  55. 
Standards,  55,  506. 
Star  gauge,  55. 
Storage  magazine,  55. 
Storehouse,  55,  424. 
Storeroom,  55,  421. 
Storm  flag,  55. 
Strategy,  55. 
Strength,  55. 
Striking,  angle,  55,  95,  274. 

energy,  55. 

velocity,  55,  102. 
Subcaliber: 

ammunition,  255. 

gun,  184,  187. 

platform,  55. 

practice,  186. 

quadrant  scale,  56. 

tube,  56,  184. 
Submarine : 

boat,  56. 

signal  flag,  56. 

defense  equipment,  56,  417. 

defenses,  56,  414. 

mine,  56,  414. 

plotting  board,  328. 
Substitutes,  515. 
Superior  slope,  56. 
Supplementary  station,  56. 
Supports,  coast  artillery,  15,  66,  76. 
Surface,.  56. 

Surveyor's  transit,  56,  314. 
Swell  of  muzzle,  56. 
Switchboard  panel,  224. 
Symbol  charts,  56. 

Table  of: 

angular  distance  of  Polaris,  443. 
blank  ammunition,  263. 
built-up  charges,  257. 
civil  dates  or  epochs,  442. 
deflections,  533. 
detonating  fuses,  302. 
diameters  of  searchlight  beams,  404. 
dimensions  of  powder  sections,  259. 
effective  searchlight  ranges,  406. 
factor  of  year  and  latitude,  443. 
interchangeability  of  subcaliber  guns, 
185. 


562 


INDEX 


Table  of,  longitudinal  deviations,  527. 

mortar  zones  and  velocities,  327. 

muzzle  velocities  and  pressures,   105, 
255. 

penetration,  277. 

powder  charges,  255. 

triangulation  data,  451. 

velocities     and     temperatures,     105, 
255. 

wind  velocity,  miles  per  hour,  358. 
Tackles,  57. 
Tactical: 

chain,  57. 

command,  57. 

divisions,  76. 

organization,  76. 

responsibility,  57. 
Tactics,  57. 
Take  cover,  57. 
Tangent,  57,  106. 
Tangent  of  an  arc,  57,  106. 
Tangential  force,  57. 
Targ,  57,  321. 
Target,  57,  525. 

hypothetical,  31. 

identification  of,  31,  503. 

indication  of,  31,  503. 

material,  35. 

pyramidal,  47. 

vessel  tracking,  57,  304. 
Target  practice,  505. 

arbitrary  deflection  correction,  531. 
Team  work,  505. 
Telautograph,  57,  345. 
Telephone,  57,  346,  515. 

operator,  78,  348,  503,  515,  541 
Telegraph  joint,  419. 
Telescope,  adjustment  of,  306. 

leveling,  305. 

orientation  of,  308. 
Telescopic  sights,  57,  168,  361. 

adjustments,  373;  385. 

adjustments  at  forts,  392. 

care  of,  374. 

for  disappearing  carriage,  371. 

for  rapid-fire  guns,  362. 

method  of  assembling,  372. 

Scott,  375. 

use  in  gun  laying,  384. 
Ten-inch  gun,  57,  120. 
Tents,  547. 
Terrain,  57. 

Thawing  explosives,  58,  266. 
Theater  of  operations,  58. 
Thermometers,  58,  353. 


Theoretical  range,  58. 
Theory,  and  principles,  66. 

of  probability,  58. 
Three-inch  gun,  58,  155. 
Throttling  bar,  58,  194,  204,  238. 
Tide  gauge,  58. 

indicator,  58. 

observer,  545. 

station,  58,  545. 
Time,  fuse,  58,  297. 

interval  bell,  58,  343,  513. 

interval  clock,  343,  515. 

interval  recorder,  58,  357. 

of  flight  scale,  58,  332,  514. 

range  board,  58,  398. 
Tool  room,  59. 
Torpedo,  59. 

boat  destroyers,  59. 

boats,  59. 

detonating  Pierce  fuse,  59,  302. 

shell,  59,  275;  276. 
Towing  target,  59,  536. 
Tracer,  shell,  54 
Tracking,  59,  323. 
Trajectory,  59,  93,  95,  96. 

rigidity  of,  96. 
Transit  instrument,  59,  314. 
Travel  of  projectile,  59,  517. 

of  target,  59. 
Traverse,  59. 

slope  or  wall,  59. 
Traversing,  speed  of,  225. 
Traversing  indicator,  60. 

mechanism,  187,  508. 
Tray,  60. 

Trial  shots,  60,  520,  529,  530. 
Triangulation  of  base  lines,  etc.,  437. 
Trinitrotoluol,  60,  269. 
Tripping,  60. 
Trolley,  60. 
Truck : 

ammunition,  60. 

platform,  60. 

recess,  60. 
Trunnion,  60. 

band,  60. 

hoop,  80. 

sight  bracket,  60. 
T-square  scale,  338. 
Tube,  60,  82. 
Tug  observer,  60,  536. 

officer,  60,  536. 

signals,  538. 
Turk's  head,  418. 
Twelve-inch,  gun  60,  110. 


INDEX 


563 


Twelve-inch  mortar,  60,  119. 
Twist  of  rifling,  60,  87,  Chap.  V. 

Union  jack,  60. 

Unit,  61. 

Unrestricted  fire,  61.  401), 

Velocity,  61,  105. 

corrections,  532. 

initial,  105. 

instrumental,  93. 

muzzle,  91,  93,  327. 

normal,  105. 

of  combustion.  61. 

of  rotation,  61. 

striking,  55,  102. 

table,  105. 

translation,  61,  93. 

trial  shots,  52'.). 

variations  in,  519. 
Vent,  61. 
Ventilators,  61. 
Vernier,  61. 
Vertex  of  angle,  61. 
Vertical,  61. 

angle,  61. 

base  system,  61,  310. 

plane,  61. 
Vessel  chart,  61. 


Vessel,  symbols,  547. 

tracking,  61,  323. 
Vickers-Maxim  gun,  61. 

Watchers,  searchlight.  78,  406. 

Waterfront,  61. 

Weights: 

of  guns,  Chap.  V. 

of  powder  charges,  259,  520. 

of  projectiles,  Chap.  V.,  520. 
Wheeled  mounts,  61,  168. 
Wig- wag  signals,  541. 
Winch,  61. 
Wind,  component  indicator,  62,  341. 

effect  of,  98. 

vane,  62,  544. 
Wireless  communications,  542. 

operator,  78. 

stations,  62. 

Wiring  system  of  carriage,  227. 
Worm  wheel,  62,  106. 

Xylol,  62. 

Zero,  62. 

Zone  energy,  62. 

mort.  62. 

of  fire,  62. 
Zones  and  velocities  of  mortars,  62,  327 


